hesitation under load - PeachParts Mercedes-Benz Forum

coachgeo · #1 06-07-2003, 06:04 PM

I tried a search but the variables to search under are endless. The few I used came up with nothing.

ok..... again. dont hate me... I'm asking here cause odds are the folk in the Datsun/Nissan forums don't know squate about Diesels. I suspect this is a generic diesel question.

I have a 6cyl NA diesel fuel injected Datsun Maxima Sedan w/auto tranny. 80 HP, 2793cc. 117,000 miles.

Accelerating on flat ground is fine, Acellerating from stop is fine.

Underload even long "slight" up grades feel like it is hesitating, and at times it feels like it bogging while all the cars are passing me. I cant give exact speeds cause the spedometer does not work correctly, but my guess is maybe Im doing 40-45mph with my foot on the floor and everyone else doing 65 or higher with out hesitation. I know of only one person with a simular Ratsun ( a diesel Datsun waggon same era) and I will ask if their performance is simular.

I have just done fuel mainatainance on it. New filters and drained the tank. No signs of algae anymore; ifffff the old problem was algae. Old problem was the same as now but way more pronounced. It would not go up an upgrade pretty much at all. The air filter seems ok. Its old but not even dirty.

I think I'll go back and retighten all the fuel line clamps I messed with to make sure Im not sucking air. Messed with=I added an inline prefilter to look for algae so there is a "few" more clamped areas air could get in than before.

Anything else I should check? I have manuels. They are not much help.

Thanks in advance

coachgeo · #2 06-09-2003, 08:38 PM

Awwww come on.... I was hoping this would be a general enough diesel question.

Anyone got a clue?

I tried an Italian tune up today. Scared the shiat out of me cause the 18wheelers were EATING my rear bumper.

Came home and did some Flooring of the accellorater in park. It did not scare me as in the RPM's were not making the motor sound wound out cause of the poor performance. Gray smoke for sure......

then all the sudden I got a WOOOPHHHHHH of gray white and brown smoke that made a cloud big enough to choke a football team... ok.... not that big but lease it would have smoked out the cheerleaders. That has made me nervous. Car still purrs like a kitten at idle and when driving at city speeds. (up to about 40mph)

I may have to drive this car to FL soon... I hope someone has a clue...

DieselAddict · #3 06-09-2003, 08:59 PM

I would do a compression test and check the injectors for proper spray pattern and opening pressure. If everything checks out, and you still have the problem it might be the fuel pump. If it's unable to pump enough fuel it will starve the engine when it's under load, such as when going uphill. Good luck.

coachgeo · #4 06-09-2003, 09:19 PM

Quote:

Originally posted by DieselAddict
I would do a compression test and check the injectors for proper spray pattern and opening pressure. If everything checks out, and you still have the problem it might be the fuel pump. If it's unable to pump enough fuel it will starve the engine when it's under load, such as when going uphill. Good luck.

hmmmmm what can I expect on a price to have this done? I dont have the equipment. I can buy a compression checker I guess. I have one for a gasser but not a diesel.

Can I remove the injectors and take them to a shop for testing? I'm reallll low on funds..

DieselAddict · #5 06-10-2003, 01:11 AM

Doing a compression & injector test cost me 2.5 hours of labor @ $70/hr. Regardless of whether you have the funds or not it makes sense to start with the cheaper stuff. Running a can of LubroMoly Diesel Purge through the injectors might help. If not and if you have the know-how you can pull out your injectors and at least visually inspect them and clean them if necessary. Did you inspect all your fuel hoses, especially those that carry unfiltered fuel? Maybe they're plugged with algae too.

coachgeo · #6 06-10-2003, 01:31 AM

I cleaned the crap out of the system with cheap diesel additive at way over prescribed ratios.

I can pull injectors if its like a complicated verson of pulling spark plugs. I just replaced the rear A arm on the car too.

P.E.Haiges · #7 06-10-2003, 09:50 AM

Coachgeo,

I would go the lowest cost way and replace the filters first. You could still have some algae in the tank or lines that plugged the filters.

If changing the filters doesn't solve the problem, your present filters are OK and you can keep them for spares.

P E H

coachgeo · #8 06-10-2003, 10:08 AM

I'll try,

The clear filter looks fine from what angle and light I get to see it from. I'll pull it first and look closer.

I found a way to get to the fuel pick up thru the trunk just the other day. I assume that is what the access hole is. It may be for the fuel pump....... but if I can get into the tank from there I want to check the tank screen.

coachgeo · #9 06-11-2003, 09:54 PM

Well I peared best I could at the semi clear prefilter and it's just do damn hard to tell anything since it is really notttttttt clear. So I next pulled the water drain from the bottom of the fuel filter and low and behold a SMALL amount of particles came out with diesel that could well be algae. So I reallly think this is my performance issues.

So here is the plan. After nearly two days of searching around town I found that in December one of the truck stops bought someones over stock of a biocide. A pallet full and sold each bottle at $1.29. Offfff course........ they were out by now. Finally I found that West Marine carried a biocide, two kinds infact. One had a great 5 dollar refund if you buy it with their fuel stabilizer too. Cool.... since they are $17 and $14 and I'm happily unemployed I'll take that. A quick look at the refund info showed.. expries Sept of 2001..... grrrrrr.... I put the bottle of fuel stabilizer back and just kept the biocide. The nice sales person gave me 5 dollars off for letting her know. That and cause I pulled all the refund lables off the neck of the other bottles for her.

Ok.... so..... I used a medicine tea spoon dispencer and some math to calculate out how much of the stuff I need (1tea spoon per 5 gal) and I mixed it with the diesel I just put in my military can. I then transfered that into what is in the tank for a total of about 13 gal.

Next step..... some time back I bouht four cylonic diesl fuel filters for a future project . The kind that are like 130 buks and they spin the fuel to sepperate water and particles like a centrafuge.

I got the four for about 25 bucks a piece from a guy who had some on e-bay. I offered to buy a small bulk of them and since he had only 4 left I got a good deal. Two are way to large. Ones like farmers would use connected between their personal diesel/Kero storage tanks and the dispense nozle. They need a minimum of 5 gpm to opperate. The other two are just on the verge of too big for a car when you look at the GPM's and the bulk size. Minimum 0.5 gpm

After talking to the manufacturing we decided since this car should push at minimum just enough diesel to fall about right at the minimum gpm's required; this will be enough to make the thing work to spin out the algae. Ifffff I can get it stuffed into the engine bay or trunk . Well I think I can in the engine bay, trunk.... I dont see it. I sorta have it mapped out and partially prepared for installation. I have to move everything around but I think it will go. I also bought a universal GLASS prefilter with swapable filters that go in it. This will certainly give me a better view.

I'll update yall on the results.

coachgeo · #10 06-12-2003, 08:26 PM

Yesterday I added the biocide.

Regular filter attached to side of cyclonic RCI Purifier filter. I just sandwiched the bracket for the stock filter in between the cyclonic filter casing and the clamp that goes around it. The cyclonic casing is very strong.

The whole shooting match. Here in the bottom left corner you can see the glass prefilter, in the middle the white stock filter, and to the right of that the RCI Purifier cyclonic filter; it’s about foot long and 6" in diameter. This one is not really made for a car as described in the previous post. I added a little mechanics wire to help keep the stock filter from vibrating out of the clamp it is sandwiched in.. and also to catch it if it does.
Final results netted:

1. I now have full power at all speeds. I did an Italian tune up and low and behold not only did I keep up with traffic. I was PASSING them on the interstate.
2. I did not get stopped by the cops
3. Feeling of accomplishment in tuff times

This is a before shot of the glass filter. I did not take an after Italian tune up shot cause....... IT LOOKED EXACTLY THE SAME!!

Plausable reasons for the results
1. The algae exist and the RCI Purifier is kicking its butt and keeping it out of the prefilter and main filter.
2. I had a tiny air leak some where last time and this set of work just happened to fix it.
3. the 6" length of 1/4 fuel line I used previously to add the first "not so clear" prefilter I used caused to much restriction to go higher speeds. The car has a metric verson of 5/16 fuel line.Any comments on this would be apppreciated.
4. The answer is (D) all the above?

When I drain the RCI Purifier in a month or so I'll post the results. You never have to replace this filter. You just drain it of the muck, blow it clear with air if needed, then refill it with fresh diesel. Will be interesting to see how much algae comes out. I will continue to treat all incomming fuel for algae till my bottle is used up. (it treats 250 gal)

THANKS FOR ALL THE HELP

Wasuchi · #11 06-12-2003, 08:44 PM

I didn't see this anywhere so I'll add....... I wonder if you have a lift pump/pusher pump somewhere? If you do it might not be pushing enough fuel now that it's getting older and starving the engine when it has a load on it.

coachgeo · #12 06-12-2003, 08:47 PM

This is a very bad focus picture of what once was the yellow gold filter inside the "not so clear" prefilter. While the focus sucks... the color is still right on. There was no floating spore looking things in the filter that I could see when it was on the car. The shadows and dark color of the car made it very hard to determine if the prefilter was yucked up or not. It took me cutting the filter out to determine that "sure nuff" its clogged. I tried to get pics of the inside but couldn’t. Inside there was a few large chunks of Algae, rust or ???

Conclusion.... The new "not so clear" prefilters SUCK. Don’t even consider it. Find a clear one.

coachgeo · #13 06-12-2003, 08:51 PM

Quote:

Originally posted by Wasuchi
I didn't see this anywhere so I'll add....... I wonder if you have a lift pump/pusher pump somewhere? If you do it might not be pushing enough fuel now that it's getting older and starving the engine when it has a load on it.

I think pump was mentioned buttt.... no longer a consideration. after the above work the thing runs like a charm. Will see if it stays that way which should mean the cyclonic filter is keeping the algae out of the regular filters. The manufacturer did say when I talked to him; no not a rep.... the owner of the company, that the cyclonic should remove the algae.

coachgeo · #14 06-13-2003, 10:34 AM

Quote:

Plausable reasons for the results
1. The algae exist and the RCI Purifier is kicking its butt and keeping it out of the prefilter and main filter.
2. I had a tiny air leak some where last time and this set of work just happened to fix it.
3. the 6" length of 1/4 fuel line I used previously to add the first "not so clear" prefilter I used caused to much restriction to go higher speeds. The car has a metric verson of 5/16 fuel line.Any comments on this would be apppreciated.
4. The answer is (D) all the above?

Well, is reason 3 plausible? Could have the 6" or so of 1/4" fuel line compared to everything else using 5/16ths have restricted fuel flow enough to cause problems at highway speeds?

Any thoughts on the other plausible reasons?

DieselAddict · #15 06-13-2003, 12:45 PM

I'm glad you have solved your problem. Of the 4 reasons you listed I think #1 is the most likely and #2 is a possibility. As for reason #3 I highly doubt a 1/4'' hose would cause too much restriction if a 5/16'' hose works fine. The difference is only 1/16 of an inch.