87 300TD will not start when hot - Page 2 - PeachParts Mercedes-Benz Forum

justinperkins · #16 04-25-2007, 12:23 AM

Quote:

Originally Posted by oniondip1

The return fuel line? Would you remove it at the main fuel filter? What should I see while cranking? Should the return flow be steady, and if it is not, how do you fix it?
Thanks

No, don't remove it at the filter, remove it where it attaches to the metal line. That way you'll have a length of fuel line that you can hold and direct away from the vehicle/engine (or into an empty container).

You should see fuel squirting. I don't think it will be steady, but never tried before. You should see fuel, at least.

If it's not flowing, you've got a fuel flow problem. It could be a vapor lock like others have suggested, it could be a valve getting closed in your greasecar kit like you suggested, or it could be a clogged fuel filter/line.

Difficult to determine at this point.

oniondip1 · #17 04-25-2007, 12:37 AM

OK, I'll give that a try as well tomorrow. The thing that gets me though, is the fact that it only happens when the engine is hot. The fuel filters are brand new, and it has with a ton of power when it is running. If I wait two hours to start it...no problem, if I wait less...no go.

robhybrid · #18 04-27-2007, 01:49 PM

I have the exact same problem on one of my cars. I tracked the problem to the vacuum valve in the ignition switch. The way to tell is next time it happens, disconnect the vacuum line going in to the top of the IP, as stated before. The stop button won't be depressed. If this is your problem, the line will be hard to disconnect, because it's under vacuum, you'll hear the vacuum escape, and then your car will be able to start.

oniondip1 · #19 04-27-2007, 02:43 PM

Thanks, I have not had time to do any work on the car this week, but am going to test that this weekend. If it is the valve, would it be difficult to replace?

oniondip1 · #20 06-01-2007, 09:54 PM

Hello all, I have finally found some time to work on the car. I have done the following:
Replaced the return fuel check valve at the injection pump
Rebuilt the lift pump
Cleaned out the fuel tank vent valve-it is clear and working as advertised
Replaced all rubber fuel lines, up front and at the tank
Isolated the Greasecar system, it is not currently plumbed into the fuel system
replaced both fuel filters and associated o-rings

The car still fails to start when the engine is hot!?!
Am I in the market for an injection pump rebuild? Could it be the injectors? I have replaced the seal washers between the injectors and the head but have noticed some fuel wetness where the injector halves come together. Any help from the forum would be much appreciated. Thanks.

jim16671836 · #21 06-01-2007, 10:06 PM

Have you checked to see if fuel is flowing back thru your return line. If so then I would disconnect the supply and return lines and using a gallon container full of diesel I would submerse both of the hoses and see if the engine will run... Jim

oniondip1 · #22 06-02-2007, 12:27 PM

I have checked the return flow, there is not a lot of fuel movement while cranking but there is some.

michael cole · #23 06-02-2007, 01:17 PM

i would recommend a compression test.

oniondip1 · #24 06-03-2007, 12:49 AM

I have had a compression test done, I don't have the numbers in front of me but they were all in the mid to upper 300's with little difference between cylinders. The shop said that it was good and to validate the test, it started this winter below 0 F without a block heater.

Could there be anything to the injectors leaking between the injector halves?...just grasping at straws here.

yandra · #25 06-13-2007, 08:30 PM

Since this discussion seems to have ended, I'm wondering if you ever solved the problem. I have the same car and exactly the same problem. It's been testing my patience for over a year!

BTW: I can start mine by spilling a liter of water on the IP and fuel filter. So temperature seems to be the issue.

michael cole · #26 06-14-2007, 09:25 AM

Quote:

Originally Posted by yandra

Since this discussion seems to have ended, I'm wondering if you ever solved the problem. I have the same car and exactly the same problem. It's been testing my patience for over a year!

BTW: I can start mine by spilling a liter of water on the IP and fuel filter. So temperature seems to be the issue.

Very interesting.i wonder if the fuel preheating system could be responsible?im talking about the factory installed preheating system.very easy to bypass for a test

oniondip1 · #27 06-15-2007, 11:00 PM

Sorry all, I have been out of touch on business for a while, finally back to my computer. I have not solved the hot start issue yet...my patience is nearing its end. I've talked with some diesel shops in the area and they have convinced me to take my IP in for testing. They have seen this type of problem with other diesels, they even have a name for it-the dreaded "hot hard start".

The theory follows...hot fuel with its lower viscosity is not being pumped with enough pressure to pop the injectors. when the engine is cold, and more importantly, a cold injection pump, the fuel is thick enough to come up to pressure through the IP. For what its worth, I have tried running this thing with the fuel heater bypassed. There was no difference in the hot start. It simply won't go when hot.

Could someone tell me why it will run when hot but not start. Does it have to do with the higher RPM when it is running, or the fact that it is using fuel quickly enough that it does not have time to sit in the IP and heat up? Does this IP theory hold water? I hope I'm not in for a costly rebuild!

Thanks again for all the replies,
Mike

#28 06-15-2007, 11:51 PM

603 fuel injection pumps break. unlike the 617 pumps. I have seen 3 already that had issues.
the 603 is a POS and no longer backed by MB because they too see it is crap.
nice engine to have when it runs good though.
check your pump.

777funk · #29 06-22-2007, 02:17 PM

My guess is that it's an electronic problem. I don't know the 603's injection pump but if it gets hot and quits I really think it's something electrical. I don't know why mechanically heat would mess up your injection. I know on my 603 there's a bunch of electronics on the back of the pump. I don't know if it's got any solid state stuff in that pump but if so, solid state devices only last so long under heat. Think about your computer's microprocessor. When it over heats your computer A. Turns off or B. Breaks.

So... That's my guess. The dealer told me the electronic stuff is emissions related. I don't know but I do know that electronics can wear out. I'd look into it. Maybe talk to a dealership in a large city about your problem. See if they know anything. GM's 6.5 liter diesel had many many heat issues on their injection pumps. Get hot and wouldn't start. I've not heard this much with MB's bosch pumps but it's possible. Maybe.

777funk · #30 06-22-2007, 02:17 PM

My guess is that it's an electronic problem. I don't know the 603's injection pump but if it gets hot and quits I really think it's something electrical. I don't know why mechanically heat would mess up your injection. I know on my 603 there's a bunch of electronics on the back of the pump. I don't know if it's got any solid state stuff in that pump but if so, solid state devices only last so long under heat. Think about your computer's microprocessor. When it over heats your computer A. Turns off or B. Breaks.

So... That's my guess. The dealer told me the electronic stuff is emissions related. I don't know but I do know that electronics can wear out. I'd look into it. Maybe talk to a dealership in a large city about your problem. See if they know anything. GM's 6.5 liter diesel had many many electronic heat issues on their injection pumps. Get hot and wouldn't start. I've not heard this much with MB's bosch pumps but it's possible. Maybe.