'95 E300 won't start when hot. Any ideas? - PeachParts Mercedes-Benz Forum

ROLLGUY · #1 07-18-2010, 05:19 PM

When my 1995 E300 is parked after driving a while (hot), it will not start. It just cranks and does not even want to start. I was able to get it started today after lunch by removing the air intake hose, and squirting WD40 in the intake. I am sure it is not glow plug related (checked glow plug resistance), but fuel related. Does anyone have any ideas? I have been running Biodiesel mostly in this one. I have searched this forum, and found no specific help. Thanks in advance, Rich

layback40 · #2 07-18-2010, 08:58 PM

I assume its a 95, not 85.
Try running it on proper diesel. It may have developed an air leak from the bio attacking the rubber in the fuel system.
Resistance checking GP's is a waste of time. You need to remove them and bench test.
Have a look for bubbles in the fuel lines.

ROLLGUY · #3 07-18-2010, 09:36 PM

Quote:

Originally Posted by layback40

I assume its a 95, not 85.
Try running it on proper diesel. It may have developed an air leak from the bio attacking the rubber in the fuel system.
Resistance checking GP's is a waste of time. You need to remove them and bench test.
Have a look for bubbles in the fuel lines.

Thanks for the reply. Yes, 95 not 85. The car starts right up when cold, so I assume I don't have a glow plug problem. I think I will pull them and check them with 12 v anyway for peace of mind, or maybe just replace them. I can see only one of the fuel lines coming from the filter that is clear (must have been replaced), and no bubbles in it. All the others are black rubber. I am not sure how to purge the fuel lines of air, as there is no hand pump like the 617's. I recently replaced the fuel filter (a few hundred miles ago), so I don't suspect it to be plugged yet. I have put 8 tanks of fuel through this car since I have owned it. I have heard about Bio cleaning out the fuel system, and attacking rubber. However, most of the posts I read about changing hoses is because they are many years old, and not necessarily because of the Bio. I have also read about a check valve somewhere in the fuel system and don't know if that would/could be the problem, or even how to test it. Anyway, all other suggestions welcomed....Rich

Biodiesel300TD · #4 07-18-2010, 10:07 PM

The biodiesel has nothing to do with the issue. If there is an air leak it's going to happen with diesel or biodiesel. Though, biodiesel may have broken down the hoses, fuel type isn't going to change anything.

My 240 was having issue with hot starts. I found it to me the connections on the starter. So I'd check all the battery and ground connections as well as the connections at the starter.

ROLLGUY · #5 07-18-2010, 11:15 PM

Quote:

Originally Posted by Biodiesel300TD

The biodiesel has nothing to do with the issue. If there is an air leak it's going to happen with diesel or biodiesel. Though, biodiesel may have broken down the hoses, fuel type isn't going to change anything.

I tend to agree with you on that point.

Quote:

Originally Posted by Biodiesel300TD

My 240 was having issue with hot starts. I found it to me the connections on the starter. So I'd check all the battery and ground connections as well as the connections at the starter.

The engine cranks just fine. It just sounds like there is no fire (kinda like a gas car with vapor lock).
I just went out after the car has been sitting for 4 hours and it started right up. I checked the glow plug system again, and it seems to be working fine. Although, I doubt the glow plugs are needed to start a hot engine.

Biodiesel300TD · #6 07-19-2010, 12:06 AM

I've worked on a couple SD's that were having hot start up issues. And it was vacuum related. I'm not familiar with your car but so I'm not sure if the vac system shuts down your engine or not, but if it does, try removing the vac line to the shut off valve in the engine bay. Then plug it back in and try starting it. The SD's I worked on, the vac took several minutes to bleeding off causing a no start or hard start issue.

ROLLGUY · #7 07-19-2010, 12:24 AM

Quote:

Originally Posted by Biodiesel300TD

I've worked on a couple SD's that were having hot start up issues. And it was vacuum related. I'm not familiar with your car but so I'm not sure if the vac system shuts down your engine or not, but if it does, try removing the vac line to the shut off valve in the engine bay. Then plug it back in and try starting it. The SD's I worked on, the vac took several minutes to bleeding off causing a no start or hard start issue.

Very interesting thought. I will try that next time.

barry123400 · #8 07-19-2010, 02:58 PM

Well the hot fuel sitting in the injection pump will bypass throught the relief valve easier. Especially if the relief valve is not really closing or seating well because of accumulated junk. So pinch off the relief valve hose and try it or close off the relief line from the injection pump by any method you like and try it hot.

It is a matter of the fuels viscosity at different temperatures. Even when the car does start and run from cold. So easy of a test to preform it should not be ignored.

This is much the same senario as the people that quote their engine will run on vegatable oil but refuse to fire off on diesel fuel. The heavier viscosity of the vegatable oil will let some pressure form or build up in the base of the injection pump. The slower flowing much higher viscosity vegatable oil back to the tank provides some head pressure in the injection pump. The same as a semi closed relief valve would produce.

Where conversly the much lower viscosity of the diesel fuel will enable freer flow of the diesel fuel through the gunked up relief valve not building enough head pressure in the injection pump to run on.

Most have assumed this difficulty of running on one fuel and not on another was always worn out injection pump plungers. I now suspect the true difficulty on many was a grunged up relief valve. Certainly the potential of worn out elements must be taken seriously as well in the alternate fuel world.

Too many in my opinion have considered it a given though in my opinion. The bottom line is some effort should be made to verify you have some pressure in the base of the injection pump with any type of situation where the available fuel has less actual viscosity from heat or type. Do the close off test even if the odds are small with your issue. It again is just so easy to preform.

I have to be careful posting possible concepts that have not been properly explored. Yet to me seem too logical to realy ignore.

What I post are probably everyday concepts to good working mechanics. I am only an amatuer part time at best mechanic. As most are on the site.

That does not negate totally what I think at the same time. To me there are many areas on these engines that some application of thought can change existing approaches and beliefs to.

ROLLGUY · #9 07-19-2010, 08:02 PM

Quote:

Originally Posted by barry123400

Well the hot fuel sitting in the injection pump will bypass throught the relief valve easier. Especially if the relief valve is not really closing or seating well because of accumulated junk. So pinch off the relief valve hose and try it or close off the relief line from the injection pump by any method you like and try it hot.

Thanks, that helps a lot. I will try it next time. Is the relief valve on my E300 the thing clamped onto a curved rubber hose just rear of the filter housing?

Quote:

Originally Posted by barry123400

This is much the same senario as the people that quote their engine will run on vegatable oil but refuse to fire off on diesel fuel. The heavier viscosity of the vegatable oil will let some pressure form or build up in the base of the injection pump. The slower flowing much higher viscosity vegatable oil back to the tank provides some head pressure in the injection pump. The same as a semi closed relief valve would produce.

Where conversly the much lower viscosity of the diesel fuel will enable freer flow of the diesel fuel through the gunked up relief valve not building enough head pressure in the injection pump to run on.

Most have assumed this difficulty of running on one fuel and not on another was always worn out injection pump plungers. I now suspect the true difficulty on many was a grunged up relief valve. Certainly the potential of worn out elements must be taken seriously as well in the alternate fuel world.

I posted on another thread about this same subject. The problem is most always at idle. Can you tell me the location of the relief valve on 617's? I also have a 190D 2.2 (not sure of engine model #) with the same problem. I've had to raise the idle so it would be a little smoother (no big deal for a stick). Also, the 617's have a "governor idle adjustment pin" (rack damper) that most always is the problem with the "paint shaker" under the hood.

barry123400 · #10 07-19-2010, 08:28 PM

Just follow the return line to the injection pump. The relief valve is what it connects to on the pump. You could easily have air ingress isues that increase when the various components warm up.

Sounds like you have your hands full with issues that checking properly might identify. For example trying the return line submerged in a small container of fluid. The fuel level should increase with cranking and there should not be air coming out as well.

If a person really wants to find out what is going on a ten dollar fluid dampened 0-30 pound pressure gauge from places like harbour freight would really help. Also it allows you to set up the system as it should be.

Two archives threads that are pretty long you could also read. Cervans relief valve and the checking for cylinder firing condition with the milli volt method. Both are methods to attempt to increase common knowledge.

Roughness at idle can be many things. If you have not adjusted or at least checked for reasonabe valve clearances on the older engines with mechanical adjustments it is a place to also start. You have enough diesel cars it will pay you dividends to become more familiar with the systems.

Most tests I mention are designed for simple application. The feedback on site indicates where perhaps the individual should go next. Then the tests may get a little more involved but you are eliminating guess work and buying parts not required to a certain degree.

ROLLGUY · #11 07-19-2010, 08:45 PM

In a way I am afraid to drive it anywhere for fear that I may not get it started when I am ready to leave my destination. I usually don't have time to fix a car or wait for a tow truck when I am out (who does?). Maybe I will just drive it around for a while and then head back and park in my driveway with tools nearby. If I get a chance to do that, I will do some tests and post the results.

barry123400 · #12 07-19-2010, 08:54 PM

Well you do need the engine up to temperature one way or another to do the closing off of the return line test. Then seeing if it will restart hot. Doing it on a cold engine will acomplish nothing.

Also if that indicates nothing then is the time to put the return line in a small container and crank the engine to make sure you are not getting a lot of air. I think the engine you are describing has a fuel heater located on the side of the engine that is notorious for developing air leaks at the hose connections.

That device would feel the engines heat especially. Some have even removed the hoses and connected them with a piece of tubing and clamps to bypass it as a test. Just to check the integity of that point of the fuel supply.

You want to see air in the return line being processed into the small container with a hot engine before going there.

ROLLGUY · #13 07-19-2010, 08:54 PM

Quote:

Originally Posted by barry123400

Roughness at idle can be many things. If you have not adjusted or at least checked for reasonabe valve clearances on the older engines with mechanical adjustments it is a place to also start. You have enough diesel cars it will pay you dividends to become more familiar with the systems.

Valve clearance is the first thing I check (and adjust) when there is a rough running/hard starting problem with these cars. Filters are usually next on the list, followed by fuel/return hoses.
The E300 and 190 have hydraulics, so valve clearance is usually not an issue. The E300 is just so much different in many ways, that I am not used to the new(ish) technology. The old iron head Diesels are have less complex systems than those in the newer cars.

barry123400 · #14 07-19-2010, 09:02 PM

The simple tests are just to either identify the problems or eliminate areas of concern. Your interpretation of them is important.

There never is any gaurantee that what has transpired on other simular cars is absolute. These are generally considered as common faults.

Once in awhile the fault is anything but common. Yet we still have to have ways and methods to localise it at least. Guessing is a terrible substitute.

I assume you have popped the fuel tank lid to check for intense vaccum when the engine has heated up. Theretically while shut down the vacuum in the fuel tank could draw the fuel back somewhat.

ROLLGUY · #15 07-20-2010, 12:18 AM

Quote:

Originally Posted by barry123400

I assume you have popped the fuel tank lid to check for intense vaccum when the engine has heated up. Theretically while shut down the vacuum in the fuel tank could draw the fuel back somewhat.

Yes, the first thing I did after trying to start it. I did not hear any air (pressure or vacuum).

In a previous post: "Two archives threads that are pretty long you could also read. Cervans relief valve and the checking for cylinder firing condition with the milli volt method. Both are methods to attempt to increase common knowledge."

I have spent the last few hours reading, I am up to page 22 of 27. I think I have "readers cramp"! I think I will be at Harbor Freight (only a couple miles away) tomorrow morning when they open to get a pressure gauge. Sounds like the best $20 (gauge and fittings) I will ever spend. Has anyone thought of putting an air chuck on the end of the "T'd" hose to bleed out the air? That way the gauge can also be moved around to check the supply and return pressures (only need one gauge). One could also make up a set of hoses with banjo fittings on both ends (and a "T" with air chuck) for testing different cars. I have several 617's, and really don't want to buy half a dozen gauges and fittings to permanently them.