I am not easily baffled, but this one has me stumped-99 E300 won't start - PeachParts Mercedes-Benz Forum

ROLLGUY · #1 02-16-2018, 12:00 AM

I am working on my friends 99 E300 TURBODIESEL OM606XXX. Background: Last week he said the engine would not shut off right away. It eventually did, and had an engine shutoff valve code. He cleared the code and the car worked fine for the next few days. He called me a few days ago and said the car will not even start now. I assumed the shutoff valve was bad, so yesterday I pulled the valve from the parts car (assuming it was good). Before I got started replacing the valve, I noticed the fuel gauge was on empty, and the reserve light was lit. I called him up and chastised him for running it out of fuel, and put in 5 gallons of B100 Biodiesel that he had on hand (he has an 80 gallon processor). After trying for what seemed like an hour to get it primed and trying to start the engine, it just would not start. With help I got it up on the lift so I could remove the bolt holding the boost pipe to the manifold. I got the manifold off, the new (used) valve installed, and again cranked the engine for what seemed like hundreds of glow/cranking cycles with a battery charger hooked up. It seemed to want to start now, like it was only hitting on three cylinders. It was smoking out of the open end of the EGR pipe, so I know it is getting some fuel. I then noticed fuel weeping out of some of the plastic fuel line connections, so I removed all the lines and went and bought new O rings for all 10 fittings. There is no more leaks now, but still no start. I thought that maybe the lift pump is bad, so a trip out to the back to harvest the pump from the parts car. I checked it before installing it, and it seemed to work (had suction and pressure). I installed it, and still no start. Each time I opened the system I pressurized the fuel tank with air, thereby filling all the fuel system with fuel. I even tested a couple fittings by removing one at a time and cranking to reveal fuel coming out of the hose. The last thing I tried was cracking each injector line, and then cranking the starter. I have fuel coming out the rear four fittings, but none out of one and two. I have worked so many hours on this car trying to get it started, that I just gave up this afternoon. I have always been able to figure out the fuel problems before, but this one has me stumped. I did check the glow plug system, and it is all working just fine. I am pretty sure the no start issue is fuel related. Could the fuel shutoff valve from the parts car be bad too? Could both lift pumps be too week to make the engine start and run? I am baffled and at a loss to know what to check short of replacing both the lift pump and fuel shutoff valve. Any ideas? Thanks in advance, Rich

Murkybenz · #2 02-16-2018, 03:18 AM

Do you have an engine oil siphon such as a Sealey or Pela ?, if so pull fuel through the system from the return line fitting where it the rubber line meets the underbody steel line at the bulkhead. Get a good flow going and it will show any air ingress / bubbles in the clear pipes.
The primary filter o ring can let air in despite sometimes having a new o ring fitted, and it is the highest point in the fuel system. Using a suction device will also bleed the system quicker than cranking and can be operated by someone while you crank engine over to save battery life.

Maxbumpo · #3 02-16-2018, 08:19 AM

Rig a new fuel source, a temporary fuel tank that is above the highest point in the fuel system, so that gravity will overcome any deficiencies in the lift pump or any air leaks in the system. If the engine will start and run, then you know you've overcome the fuel priming problem. However, you would still need to resolve the root cause.

ROLLGUY · #4 02-16-2018, 10:35 AM

Quote:

Originally Posted by Murkybenz

Do you have an engine oil siphon such as a Sealey or Pela ?, if so pull fuel through the system from the return line fitting where it the rubber line meets the underbody steel line at the bulkhead. Get a good flow going and it will show any air ingress / bubbles in the clear pipes.
The primary filter o ring can let air in despite sometimes having a new o ring fitted, and it is the highest point in the fuel system. Using a suction device will also bleed the system quicker than cranking and can be operated by someone while you crank engine over to save battery life.

I don't have anything like that, but it sounds like the best thing to do. I do have a Mityvac with the reservoir for bleeding brakes, maybe that will work? I will also replace the primary filter O ring as well, just to be sure. Thanks!

ROLLGUY · #5 02-16-2018, 10:51 AM

Quote:

Originally Posted by Maxbumpo

Rig a new fuel source, a temporary fuel tank that is above the highest point in the fuel system, so that gravity will overcome any deficiencies in the lift pump or any air leaks in the system. If the engine will start and run, then you know you've overcome the fuel priming problem. However, you would still need to resolve the root cause.

I tried that at first, but eventually abandoned that for added fuel in the tank. Once I got pressure in the tank and fuel flowing through the system, I assumed there was no problem with the tank and fuel supply/return lines. However, I may try that again anyway (with Diesel). I have a sneaky suspicion that the Bio I used was too cold, and may be too thick (only 50 degrees in the shop where the processor and car is). I may be wrong in this, as the car has been ran on this fuel for a long time without issues.

Maxbumpo · #6 02-16-2018, 02:32 PM

Oh, I see, homebrew B100. I'd be very suspicious of the injection pump and delivery valves, they may be gummed up.

Recommend #2 ULSD in a temporary fuel tank at the engine bay to be sure the engine has every opportunity to start.

ROLLGUY · #7 02-16-2018, 03:46 PM

Quote:

Originally Posted by Maxbumpo

Oh, I see, homebrew B100. I'd be very suspicious of the injection pump and delivery valves, they may be gummed up.

Recommend #2 ULSD in a temporary fuel tank at the engine bay to be sure the engine has every opportunity to start.

Agreed on the D#2 in temp fuel tank. I see a trip to my local lawnmower shop to get a used tank in my near future. Yes homebrew B100, but the car has not gotten a full time diet of the stuff. My friend does not brew during the winter, so I imagine the car has had only D#2 for the past couple months. The exception being the 10 gallons or so of B100 that has been in the processor for a couple months that I put in the empty tank to get the car started......Rich

Murkybenz · #8 02-16-2018, 04:12 PM

Use the Mityvac to pull vacuum on a large drum as the return line flow is about half a litre a minute at tickover, big drum will allow you to keep the engine running until it fills up.

ROLLGUY · #9 02-20-2018, 10:12 PM

Quote:

Originally Posted by Murkybenz

Use the Mityvac to pull vacuum on a large drum as the return line flow is about half a litre a minute at tickover, big drum will allow you to keep the engine running until it fills up.

This worked awesome! I punched two holes into a canning jar lid, and put two hoses in it. One went to the return fitting, the other to a hand vac pump. I had the supply hose in a can of new clean fuel. After pumping and seeing no bubbles in the lines, the engine started up the third or fourth crank! It did stumble a little at first, but smoothed right out. Thanks!