interpretation of compression results? - PeachParts Mercedes-Benz Forum

bfrinkus1 · #1 12-18-2011, 06:52 PM

I have a 1984 190d 2.2l 5-spd with 432xxx miles. I've owned it since 386xxx and been running an 80% WVO/20% diesel blend most of the time.

Every year when winter rolls around it's just a little harder to start, even though I make sure GP system stays up to snuff. Engine never excessively smokes and runs very smoothly with adequate power once warmed up and good economy ~35/40mpg.

Last year, I removed injectors, cleaned bodies, matched pop-off pressures, and replaced visibly worn parts with used spares in better condition. All work was done using a homemade tester, so accuracy wasn't 100%, but it allowed me to get pretty close. Despite working on injectors, starting was exactly the same as before repairs. I decided to leave well enough alone, and continued through the winter with hard starts.

This year, I could barely start it on the first day below 40f (10-20sec cranking time)and realized I wouldn't make it through the winter and ran a compression test. Hot, my pressures were 400, 440, 410, 430. After cooling off, I ran the test again cold at 40f and got 340, 410, 400, 410.

While injectors were out, I confirmed all plugs getting red hot and battery/starter sytem up to snuff.

I know my number 1 hole is a little weak, but these results are pretty good, especially given the high mileage on this engine, right?

I know that running a WVO blend may make my car start a little harder than same car running diesel, but this car used to start well!

What's the concensus opinion out there...will a set of new Bosch injectors restore cold starts to a serviceable level?

Thanks for your thoughts!

Best,
Brad

tangofox007 · #2 12-18-2011, 07:25 PM

Checked injection timing lately?

79Mercy · #3 12-18-2011, 08:57 PM

I would imagine that WVO at 30 degrees is a little thick

Biodiesel300TD · #4 12-18-2011, 10:51 PM

Quote:

Originally Posted by 79Mercy

I would imagine that WVO at 30 degrees is a little thick

I agree, cold VO is much harder to burn. An 80%WVO / 20% D2 is going to be very thick at 40 degrees with no heaters. If your low temps for the day are in teh 40 I'd be blending down to a 80/20 WVO/D2 mix during the winter. If your high temps are 40 then I'd be running straight diesel.

vstech · #5 12-18-2011, 11:23 PM

#1 and #3 are quite a bit lower than the others... I'd soak them in Marvel Mystery Oil for a few days and see if the number improve...

bfrinkus1 · #6 12-19-2011, 08:42 AM

thanks for all input so far. To address replies:

-I don't know how to check injection timing. Hot link to instructions?
-re WVO, same car running same blend started much easier a few years ago. Also, my 300d started and drove great at 30f this AM running same blend. Been running wvo for 8 years and familiar with cold weather behavior. HardER starts? Sure. Hard to start period? Not normal.
-re marvel mystery oil, how to do it? Pull injectors back out and fill through injector hole til full? Since this will eventually seep by rings into crankcase oil, should I plan on changing oil after trying this treatment?

Again, thanks all for your time and opinion!

Best,
Brad

GregMN · #7 12-19-2011, 10:47 AM

The problem may lie with your IP, not the cylinders or injectors. The IP may provide enough pressure to run the car, but not enough at starting RPM's to start the car. This may be aggravated by the thicker fuel.

Have you tried ditching the bended fuel and running a tank of diesel ?

What part of the country do you live in ?

barry123400 · #8 12-19-2011, 11:21 AM

Quote:

Originally Posted by GregMN

The problem may lie with your IP, not the cylinders or injectors. The IP may provide enough pressure to run the car, but not enough at starting RPM's to start the car. This may be aggravated by the thicker fuel.

Have you tried ditching the bended fuel and running a tank of diesel ?

What part of the country do you live in ?

This is more or less what I was wondering as well. Basically the elements gettinga little tired or delivery valves not really clean. So much depends on both how clean the fuel is and what contaminates where in it. You should have a water trap installed in your situation in my opinion. Maybe you do.

ah-kay · #9 12-19-2011, 11:33 AM

The compression numbers look decent. Car should start easy with 100% WVO down to about 35-40F-ish. It may not stay on well but it should start. 80/20 mix should start and stay on without any problem.

Try to take the WVO out of the equation by hooking up a bottle diesel under the hood. Purge the WVO with engine running and then leave it overnight. If it is still hard to start then it is something to do with car.

Good luck.

Biodiesel300TD · #10 12-19-2011, 11:39 AM

Though your compression numbers aren't totally even I wouldn't suspect them in a hard start issue. The unbalanced numbers will cause rough idle, but I wouldn't think they'd cause starting issues.

When is the last time you changed filters, or did a Diesel Purge. The Diesel Purge will clean out any buildup in the fuel system. Run it straight from the can. Also are you sure you starter and battery are up to snuff. The starter might be turning a little too slow with the cold, making it harder to start.

Zacharias · #11 12-19-2011, 11:48 AM

I don't think you have any issue with your motor, especially for that mileage.

The issue is that (if I understood you correctly) you're starting your car with the blend. You didn't mention if you have any additional heat for the fuel supply, so I assume not.

If you are actually getting it started at 30 F with those miles, with that blend, frankly you're doing great.

If anything has changed I'd suggest that you're simply seeing the incremental affect of slightly increased engine wear over time making it harder to start on that mixture. It will continue to degrade with time.

Disclosure: I'm a two-tank WVO believer so I'm not hot on blends theories to start with. As far as I am concerned, you are feeding your injection pump, injectors and motor something that's slowly killing them, then asking us "Why is my motor not like it was a year ago?"

Eat McDonald's for lunch every day for the next year then let us know how your'e feeling

EDIT: I suggest you read: How do I avoid problems with my VO conversion? - Plantoil/diesel conversion basics

... with particular emphasis on combustion issues and the required injection temp for WVO.

bfrinkus1 · #12 12-19-2011, 05:06 PM

It might be time for a can or three of diesel purge. I could then rig up a temporary D2 tank to flush system and try a D2 only cold start on. This could eliminate or prove fuel source as the problem and it probably needs the diesel purge anyway!

I'm compulsive about changing inline filter as needed (I visually check it along with fluid levels every weekend), and change my spin-on filter with OEM stuff every 2000miles. I could go longer, but filters are a cheap and easy way to stay off the side of the road and prevent unnecessary wear and tear on my fuel system.

While I sense skepticism from some, it's nice to see a civil discussion about WVO feasibility. I've done 2 tank systems (converted an 82 240d, sold; converted an 84 190d, died a rusty death; and purchased a preconverted 1984? Ford Ranger, sold), and while very functional, I believe they are unnecessary given the toughness of our engines. I also dislike the idea of adding weight and complexity to the simplicity of our wonderful cars! Losing trunk space is a drawback for most systems too.

Our cars were designed to run on D2. However, the D2 available in the early 80s was 5000ppm sulfur! The crap we get now is 15ppm and provides piss-poor lubricity compared to the stuff of old and is ultimately not the same fuel. Additionally, I believe that MB owners manuals OK the use of blending D2 with unleaded a la 10-20% for cold weather operation. This is to say that I reject the notion that WVO is an unsuitable fuel simply because it was not what the engine was designed to run. If it's clean (this IS critical regardless of fuel type) and it's combustible and it'll flow, these cars will happily run down the road!

I have heard reports of piston rings getting gummed/coked up with carbon/WVO residue. While my compression numbers aren't perfect (larger variation than I'd like...), I think that simply having 432xxx total miles with the last 50xxx miles on WVO blend disproves the absolute theory that WVO=trashed engine.

All told, I probably have about 300,000mi on WVO with several vehicles reaching ~50,000mi on my blend. Knock on wood, this is the first problem I've ever had (other than clogged filters early on) with a fuel system. I credit good oil and a fuel filtration system half engineered by me and half purchased from Charlie Anderson of Greasel fame for keeping me largely trouble free.

Taking all advice and gonna see if I can use it to get the car back on the road again.

Thank you all for your time and expertise!
Brad

Zacharias · #13 12-19-2011, 05:37 PM

Quote:

Originally Posted by bfrinkus1

I think that simply having 432xxx total miles with the last 50xxx miles on WVO blend disproves the absolute theory that WVO=trashed engine.

My comment was not "WVO=trashed engine". The accepted knowledge is BAD WVO technology= trashed engine. You aren't actually using any WVO technology whatsoever, so you've chosen the fast lane of the polymerization highway.

You are proving the toughness of both the engines and the pumps in the fact that the car is doing so well on the concoction you're using in the tank.

Saying the car runs on it, isn't a technical endorsement. Having faith doesn't counter the accepted technical know-how in this area, which is briefly introduced in the link I posted above.

Biodiesel300TD · #14 12-19-2011, 06:26 PM

Bucket #1 might have a slightly stuck ring as stated before. If you want to try the Marvel Mystery Oil(MMO) (brake fluid works great too, that's what I've used), just dump a ounce maybe two into each cylinder through the injector hole. Let it sit as long as you can. It will drip by the rings over time, so an oil change is a good idea, at least if you use brake fluid, I'm not sure about MMO.

vstech · #15 12-19-2011, 10:07 PM

Please keep the topic on the compression, and information on that subject.
if you wish to discuss WVO/SVO/Blend or anything but diesel, please start a new thread in the alternative fuels forum! That's what it's for!

I can either move all the VO discussion to that forum, or leave it here, but don't discuss it in DD! thanks!