617 Gwagen low on power...
 

OK bit of a stumper here....

I drove another 300GD cabrio a few weeks back and realized that I have been down on power since I bought the truck (I never had a basis of comparison so I never realized)

In order to check the tank strainer I ran diesel purge directly from a bottle under the hood and noticed only a little improvement afterwards. (And no drastic change while driving either)

Getting frustrated I dropped off my truck last week to my Mercedes mechanic to go through a few things to see if we couldn't sort of the source of the problem. He did a valve adjustment and tested the injectors and found that one of them was 'pissing'. He also checked the timing chain for stretch (Just a small amount) and he put in a new chain tensioner, fuel priming pump and injector. I also put in new fuel filters. Hoping that I had cracked the nut I was disappointed to see a maybe 10% improvement. The truck has a bit more pep and responds a little bit better. So at least i'm getting somewhere.....here is where things get odd though.

My mechanic mentioned that after buttoning everything up that he had a hard time getting the truck restarted (I never had a problem with this before) It would crank and cough a bit but it took a lot of cranking to get it going. I didn't think much of it at the time because when I picked it up it started perfectly. (And a few more times throughout the day)

Last night however while leaving work I cranked the engine and it started with a bit of a stumble but then died after idling for about 5 seconds. I primed the heck out of the pump two times and it wouldn't even start. At this point the truck was parked uphill so I turned it around to more level ground and after another attempt was able to get it going. This morning, same problem. I said "Alright, fuel flow, that tank strainer must be clogged." The screws on the access panel were so bad that I had to drill them out and what a mess underneath it....There was so much dirt, grime and particles under the panel that I couldn't even see the lines. I vacuumed everything out and ran straight into problem #1. I don't think I can even get the lines off....and even if I do I will probably breaking them. (As is what happened when I removed the sending wire.....one connection snapped right off.

My girlfriends father who was helping me came up with the idea of running compressed air down the lines to unclog it. I should note at this point that priming the pump didn't seem to be drawing much fuel but after blowing the lines it seemed to be flowing much better. It still took some doing and we cracked the injector lines to remove any air but the truck eventually started again.

My girlfriends father thinks I might have a weak injection pump. I'm still on the thought of clogged strainer.

Any thoughts will be highly appreciated. (I have a few pictures which I can upload tomorrow)

What about the fuel pump?

- Peter.

Replumb the engine to run off a 2 liter bottle of diesel in the engine bay. Sluggishness gone, then its an issue with lines or tank. Sluggishness remains, the issue is on the engine side

I thought it might be a hole in a fuel line on the suction side letting in air.

Swap inlet and return lines and see what happens. If the situation resolves it's probably a plugged screen. But since you already ran the truck on a bottle of fuel, it doesn't seem that this can be the problem.

Update

I had a tough time starting it again while leaving work (The longer it sits the worst it gets) a mix of some serious priming and holding the pedal at full throttle finally managed to get the engine running and holding. This time however while I was priming I noticed that I was getting air bubbles from the top bolt on the main fuel filter (Which made me absolutely furious :evil: ) I didn't have an adjustable wrench on me so I left it alone till I got home. When I did get to it I got a good 4 turns on the bolt so air was definitely getting into the system right there. I also noticed that a return line on my injectors was routed under the throttle adjustment rather then over it and was a bit kinked (Which also didn't make me smile)

Now I should mention that I do trust this mechanic. Factory trained with a good 20 years experience 90% of which has been on Mercedes at the main local dealer. He went independent a few years back and he did a flawless head gasket job on my SDL some time ago. I think the difference is that on that job HE did the work but that this job was done by one of his employees that he has since hired.

I will try to start it first thing in the morning and should know in about ten seconds if that was the source of the hard starting. (Fingers crossed)


Back to the lack of power issue and to recap on a few things.

1. When I ran diesel purge a few weeks back I did it from a bottle under the hood and there was no difference in performance. (Starts to rule out a clogged strainer or line.)
2. The tank leaks above 50% but I have never seen it leak from the seem so it is possible that the leak is from a line.
3. It was reported to me that my chain only has a minor stretch in it.
4. When blowing air down the lines to the tank the cap was off and I could hear the air coming through loud and clear.
5. My mechanic did a valve adjustment and installed the following: chain tensioner, one new injector, hand priming pump, new main fuel filter,(Although apparently not tightened....)
6. My Indy talked about doing the drip timing on the pump but it was not actually done.


At this point i'm still suspecting the injection pump and on a related note, I just received a used injection pump and 5 injectors from an 85 Euro 300D NA so I have a second pump which I can get tuned to spec if the need arises.

I say give up on it, cut your losses, and sell it....to me!! :)

sorry, serious G series envy.

hope you get it sorted out. keep us updated!

I'm not sure, but did you verify that the white G had the same diff ratio as you? Also didn't you have taller tires?

I don't have any idea what the different G gear ratios are and what year difference your trucks were, but let's say for example he had a 4.10 diff and you had a 3.60 diff, that could explain a huge difference in pep off the line and impression of power.

My 74 240 was considerably faster off the line than my 83 240, both with 4 speeds, and even with the 83 having the more powerful 616. The difference was all rear end gearing, but of course the 74 was a 55mph vehicle wound out, and the 83 will easily do 70.

On top of that you have your tire sizes that could be impacting the ratios. First thing id want to do is make sure my comparison was equal. What tire sizes on both trucks, what ratios on both trucks, ect, jut in case I wasn't trying to solve a gearing difference.

Were they the same years? I thought I remember the white G was very early, while yours is later?

Alright the hard start problem was resolved from the loose main fuel filter bolt (Of all the dumb little things.....)

They are pretty close; Dude's was an 80 and mine is an 82. It is possible that I had lower ratios but we checked and our trucks are identical in most respects (He has hard top switchgear and I don't, he has power and I don't, but I beat him hands down for rust :D )

Linkage hitting full stop? New style primer?

Linkage is good, the primer is a week old and of the new Bosch variety.

Cheap fix is to find another pump and swap it, if its better get the old one rebuilt. After you run it off a water bottle of diesel and verify the performance is the same. The governors are just a bunch of weights and springs, even diesel mercedes wear sooner or later.

Have you taken timed runs? Butt dynos can be very subjective taking consecutive runs. Best to drag race him.

How many miles on the engine? Have you done a compression test? Pop and balanced injectors?

The inline pump is lubricated by oil not fuel and can have a very long life if not mistreated. I doubt that is your problem.

Funny thing is I ran the bottle a few weeks back and there was no change. Someone on the Gwagen forum brought up a good point which is that I ran the bottle with the old main fuel filter and that I should run the rest again with a new filter.


Yeah timed runs are not needed.... The difference between my truck and the other 300GD were pretty drastic. I actually had trouble getting it into 1st gear because I wasn't expecting it to take off like it was. From then on every gear pulled like crazy and the engine actually reacted to inputs perfectly. In my truck I pretty much have the pedal pushed all the way down all the time.

When I bought the truck the odometer was stuck at 86,000 and the owner said it was broken for about a year. I'd say the engine has around 100,000 miles, probably a bit more. Compression is good, and my mechanic pop tested the injectors, only one was 'pissing' and has been replaced.

Check the length on the pressure relief valve spring on the Eng side of the IP. Rebuild kit for the lift pump is cheap. I have a spare ill let go for a 6pack.

At first I was going to say 'why' but I decided to do a search and now I see where you're coming from. (Seems like a pretty credible theory)

Lay beck 40 brought up a good point in this thread which I will check when I get the chance to do another bottle run.

http://www.peachparts.com/shopforum/diesel-discussion/277893-1979-300td-can-anybody-walk-me-through-lift-pump-test.html

Every 617 I have had, it has given appreciable results.

Ok here is the current situation and diagnosis.

The good news? All signs indicate that my tank strainer is at least ok and not the source of the low power issues.

First, this is the fuel that I dumped out of the main fuel filter that I replaced just the other week. (Looks pretty bad but I didn't want to jump to conclusions so I kept going)
http://img842.imageshack.us/img842/2094/9oak.jpg

This is the fuel that I used for the closed circuit test
http://img7.imageshack.us/img7/7448/myld.jpg

And this is what the return line brought back at the end of the test.
http://img703.imageshack.us/img703/897/ht5b.jpg

Here is where things get interesting though. Running off the bottle with a BRAND NEW main fuel filter had NO impact on performance whatsoever.


However before I fiddled around with the filters and bottle I decided to check the banjo bolt on the engine side of the injection pump as winmutt suggested. My spring was just around 20mm. I did a quick stretch (By hand...unscientific but this was just a test.) drove the truck and noticed better reactions to my inputs. Ok, now we're getting somewhere 8-)

I've been doing quite a bit of searching but I can't find out if anyone ever managed to find a suitable replacement spring for the banjo bolt..... (I should mention that my uncle works for a spring manufacturer and might be able to come up with something)

Here are a pair of videos of the return fuel supply which I took at the end of the bottle test.
http://www.youtube.com/watch?v=hRPDA5LwI1Q
http://www.youtube.com/watch?v=sWL5peJ4f4Q

Have you had someone sit in the wagon....while off....floor the accelerator and confirm the linkage is hitting the full throttle stop? Also not sure on a g wagon, but on the cars.....there is a firewall pivot bushing that rots and causes issues, there was also one year that Mercedes used a rubber bushing near the stop lever....which rotted....and on the euro models, where the fork goes into the stop lever....there are two plastic bushings that are usually mia and people don't know there is suppose to be a bushing there....

Already tested that. It's good.

Iirc spring should be 27mm. You can order repolacments from Bosch shops.

Does it have a part number?

(When you say Bosch shops I presume you mean general retailers? NAPA, Autozone etc?)

Bump-Does anyone know of a source for these 27mm springs?

(I can't seem to find a Bosch shop in my area)

I made and sold some adjustable fuel pressure regulators as well as fuel pressure test kits a few years ago. Not sure if I have any left. I'll look if you like.

Thanks for the offer (I just read your thread on them, nice work on the adjustable models!)

Right now however my goal is to stay as stock as possible in order to narrow down the power loss. My spring is 20mm and probably just one step in the process, once I get a new spring in and see the difference i'll be able to know where to focus next.

Just stretch the spring and measure pressure before installing.

Sad to say but I don't have a pressure gauge and i'm pretty sure that the spring would just re-compress very quickly anyways.

If you get a new spring you still have to measure it to know where the pressure is set.

Have you verified as suggested earlier that both G wagens have the same differential? Best way is crawl under and read the part number.

Yes they both have the same differentials.

That spring is not going to have that great of an impact on performance. You said compression is good ( what are the numbers?)

I would suggest verify /set IP timing next, if no help, put in a set of rebuilt injectors.

And I would look into why your tank is leaking above half full.

A thought occured to me earlier this week that I will be testing.

I know the tank strainer isn't clogged from running the bottle under the hood. I know that my timing chain only has a small degree of stretch. I know that my injectors are spraying correctly.

HOWEVER I don't know what pressure they are injecting at and I don't think my indy bothered to check anything beyond the pattern. (I'm also wondering if he even installed new heat shields)

I should have done this a long time ago but I ordered a pop tester to run some tests on my current injectors. Considering all the hassle I went through with the POs idiocy on everything else I get the feeling that I might have turbo injectors installed on my engine.

http://www.peachparts.com/shopforum/open-discussion/305584-search-has-finally-ended.html

The tester should be here later this week and will work for my 603 as well so i'm considering this a long term universal purchase :)

First of all, that's a sweeeeet G can you've got there. *nudge*nudge* nothing wrong with dripping in a 617a....

x2

For your NA:
-Injector pop pressure and spray pattern
-How stretched is timing shain?
-Fuel return stretch as others have said
-Injection pump timing (you can advance it to 26-28* listen for knocking and back it off if it knocks.
-Obvious air and fuel filter restrictions.
-If EGR is equipped, check to see if the EGR is kicking on when it shouldn't be
-Turn your ADA up juuust a smidgen
-Install a MW pump and watch it belch smoke :P

Have you ever checked the fuel pressure relief valve?

A 617a is always an option should this engine ever go. Until then however i'd like to keep it as is :)

-Chain; only a small amount of stretch. Put in a new tensioner.
-Have not checked the timing (Need to learn how to do the drip method)
-Fuel seems to be getting to the IP just fine and the air canisters on G's have a tab that deploys if there is an air restriction ;)
-The EGR crap was the first thing we ripped out :D
-ADA? You mean the ALDA? Don't think the non-turbo has one.....
-M-Pump is good enough :P

Yes, the spring is 20mm but i'm having a heck of a time finding a 27mm replacement spring. (I can stretch it by hand but it will just compress again)

I would think this might be the issue, and I would say try replacing it with the one of the newer style ones.....but googling I see they are NLA....

I have read a few people have shimmed the spring....it would be really nice if someone would make a replacement....I want to stretch mine but am afraid it will snap and I will be sol.....

The NA pump should have an ADA, it's like an ALDA but runs on atmospheric pressure instead of boost pressure. So you don't smoke when driving up a mountain.

How much is a little for chain stretch? 5*? 10*? 1*? What method was used to determine the stretch? The 'line the marks up on the cam tower' method isn't very accurate.


Again, if someone can get me a NOS spring I can get it measured for dimensions and spring rate, making it really really easy to buy off the shelf replacements.

Ok update.

I ordered and installed new monarch nozzles. They are balanced as well (I got just around 1700 psi on 4 and around 1650 on another) I had to leave #5 crush washer in as I went through complete torture removing #1 http://www.clubgwagen.com/forum/imag.../icon_evil.gif (In the end I had no choice but to chisel it out) I hated to do it like that but nothing else worked. Tomorrow when the engine is warmed up again i'm going to try and remove #5 one last time.

Results? inconclusive :( There is a bit more pep and reaction but nothing significant. One thing for sure is that she is idling a lot better (Less vibration, engine no longer shakes) So at the very least i've eliminated another area of potential problems and made her just that little bit better. I have yet to find the core of the issue and for the rest of 2013 until the spring of 2014 i'm throwing in the towel. The truck runs just fine and it moves along once I build up speed. It's just those long steep gradients that give me trouble. I'm afraid that I might just have to do a compression test even though I lack the signs other then loss of power. (If the compression is bad i'll drive her till the engine explodes and throw in a turbo motor)

Ok, thread revival but I FINALLY managed to do a compression test today.

1 320 PSI
2 360
3 380
4 360
5 365/370

These numbers were done on a hot engine with a Peachparts ordered 1000 psi compression tester.

I'm going to go outside and reassemble everything now (Only this time i'm using Grezzers injectors and not the ones I rebuilt myself the other year)

*Update*

Well at least I know that I did my injectors correctly last year. :) But just like last year I was completely unable to remove the heat shield on #5 :(

More fiddling and questions on the fuel pump if anyone can help.

I picked up a used injection and fuel pump from a 1985 300D Euro last year as a backup. I had a bit of time today to play around so I decided to try swapping out the fuel pumps in order to see if it would make any difference in power delivery since removing and installing the pumps only takes a few minutes.

I freaked out a bit once I got both units on the bench and realized that there were a few detail differences between the pumps.

The 300D pump on the left in the vice. Original 300GD pump on the right.
http://i.imgur.com/vDLgX0U.jpg?1

http://i.imgur.com/LvyY12G.jpg?1


The #1 thing i'm worried about is the plunger on the back. On the 300GD pump it's fat at the end with a skinny shaft. On the later 300D pump the shaft is the same diameter from front to back. I don't want to risk damage to the IP and I don't know if I can just swap out the shafts or not. The Gwagens shaft slid right out while the 300D shaft took some effort to remove (Probably since it has been sitting for a while.) The other stumbling block on this test is that the hand primer pump on the 300D wouldn't budge. (I'm letting the penetrating oil do it's job overnight before I try again) Any thoughts would be most welcome.

I think the thing to worry about is the end of the shaft that goes into the injection pump. If they are the same diameter, you're ***MAYBE*** good.

Have you checked EPC for the two different engines / pumps to see if the same lift pump was used in each?

If the "throw" of the cam inside the different injection pumps is not the same, then you probably can't swap lift pumps. If you can rotate the injection pump, you could put the shaft inside it's hole in the injection pump, and measure the throw as the cam pushes it in/out.

If I were you, I'd swap in the newer used injection pump complete (after replacing the primer pump) and get the timing set correctly, and then check the acceleration performance.

Other possible causes of low power: clogged air filter / restricted intake, plugged exhaust.

Did you ever check the injection pump timing?

I would also check the chain stretch using the camshaft marks method, it is close enough to give you a good idea of the condition of your timing chain.

Stuck heat shield in #5: Have you tried penetrating oil? Brake fluid also does a great job of dissolving carbon. Next, I would find a screw that can get a good bite in the center hole, screw that in but leave the head standing proud so you can grab it with a vice grips, and gently work it until free. Blue wrench (torch) may also be an option, if you heat up the entire area and then quickly cool just the heat shield it may pop right out.

60psi
 

that 1 to 3 cyl difference of 60psi bothers me.... it should not be over 45psi iirc...


.

And why did we remove the lift pump again?

These rarely go bad, and when they do...they stop working or fill your fuel tank with oil....

It always lifts fuel into the injection pump, and the the fuel pressure relief valve on the rear of the injection pump. Does the job of bleeding off pressure/fuel to keep the correct pressure in the injection pump at all times rather idle or fuel speed.

The one good ol cure for low power and as the first step....take a high speed freeway road trip....then start diagnosing....I am getting ready for another 3000 mile trip in the euro....these cars like to drive...not show off for the neighbors..

Also remember, you cannot just start pulling things off and replacing them as a cure for anything on these cars. You are dealing with age on these vehicles, and with age comes time and with time comes grime....you really have to start with the furthest away item and then move onto what is under the bonnet. With this issue you want to go from the tank to the injectors in one swoop..

Could you take the spring, stretch it to 27 MM, maybe hold it in that position for a few days, and then put it in compression equivalent to what it would experience in the IP and check it periodically to see how long it holds its length? Then you would at least know if you can stretch it for a temp fix to see whether or not it is the problem.

Greazer makes and sells a replacement overflow valve spring. I have ~1000 miles on mine, does well.

Because I struggle to do 40mph in 3rd gear up a 8% grade every time I take the truck to work. In this sense its been "Italian tuneup"ed dozens of times. (It's no garage queen) I'm doing everything I can to find the problem and the lift pump is certainly a place to look. The old fuel tank and lines had rust in them which probably caused havoc on that pump. (The pre-filter can only catch so much)

The fuel tank is brand new, are are the fuel lines along with rebuilt fuel injectors.

Good to know! I'll be reaching out to him soon :cool:

I hate to bust it to you, but this is normal. My 78 struggles to keep 45 on grades with altitude 5-7k.

My euro, which has the same engine as this and injection pump will make the same hill at 55 in 3rd. Yes it is a stick shift.

I don't know what else is on your wagon if there is an ac compressor that can drag the engine.

Also with out an ALDA you will experience tons of black smoke if you attempt to floor it to make it up a grade. Slowly n steady wins the race :P

Was you wagon ordered for the states or was in imported in the day?

I ask because they fashioned some crude egr stuff to help with pollution in the day. This can/could case a clogged intake, not enough oxygen to turn into energy etc.

Reading another thread that has a photo of your injection pump. I suppose you have never replaced the o rings on the M pump? Nor the copper washers? Also ever timed the thing as I see it appears to have never had a valve removed.

http://i185.photobucket.com/albums/x...nisch/mrsf.jpg

2 is an o ring and 5 is a copper crush washer. These being bad or the valve not being torqued correctly can also cause power issues. I replaced all my o rings with ones found in the assortment you can buy, I also bought the correct socket and torqued them down correctly. They all had bad o rings and were not tight. So I opted not to replace the crush washers.

It is also wise to learn about air density, the shortest answer is that when temps are cold there is less oxygen in the air thus it means less oxygen for a car to burn for power. Diesels really heavily on the correct amount of fuel and air aka oxygen to preform their bests.

USATODAY.com

I need to shower and coffee now :P Post pics of your engine, and closes ups....it may be easy for us who have worked on those engines to point out things that they less trained eye can see or doesn't know what it is.

I hate to toot my own horn, but owning a euro w123 has taught me a HUGE amount about how the euros differ from the us. Also my 78 being a us version...I have both examples to prob :P

.

no 2 is the ring, if no leakage no use of changing copper washer or ring either
no 4 on the other hand is delivery/performance related and if worn must be replaced....

.