Hello all,

This is my first posting on the MB side of the forums. I recently acquired a 1989 300e that has been sitting for the better part of two years and in the process of restoring it to driving condition. Alas, I am unable to get it started. To date, I have replaced:

- battery
- fuel filter
- rotor, distributor cap, plugs and wires
- air and oil filters

It turns over strongly and when starting fluid is used it will catch and run surprisingly smoothly for a few seconds before flaming out. I'm a MB newbie, but this seems to eliminate the fuel pump relay and OHP from the equation. It seems to be getting air and spark since it runs when fuel is introduced into the intake system.

So I've been trying to logically eliminate causes starting at the ends to the system and moving to the middle. I can hear the fuel pumps energize when I turn the key and am getting pressure up to the fuel distribution unit. I removed and inspected the EHV and it was wet (but not leaking). The lines to the injectors are wet, but have no pressure when the engine is turned over, so somewhere between fuel entering the fuel distrbution unit, and it leaving, it would seem that there is a blockage or input failure.

The next logical step seems to be to replace the fuel distribution unit. Before I systematically start replacing components, are there any relatively simple tests to isolate items or common gotcha's I'm missing that might help...ie..vacuum line somewhere or voltage check on xxx component?

Thanks in advance.

Dan

Maybe try testing the fuel pressure? The pumps may be running but not creating enough pressure to crack the injectors, which take at least 60psi (I think)

Or maybe whatever gas was in there for the last two years went bad and gummed every injector or other part of the injection system(long shot)

Or maybe something with the ignition switch is disrupting power to the fuel pumps when you turn the key to "start" versus "on" (here's that voltage check you mentioned)

At the very least, if there was no stabilizer in that gas when it was parked, I would drain it somehow and put in fresh gas with techron or seafoam. Todays gas with ethanol in it does not last!

I'm no expert, but I hope this helps
Im sure others will chime in with plenty of ideas, this is a great forum!

-Chris

__________________
Streetside: 1987 Mercedes 300E Petrol Blue/Green
2014 Ford Mustang Grabber Blue
1999 Ford Ranger Green

Dockside: 1968 Eltro 17
1985 Silverton 34C

And by the way, the OVP's can create all manner of strange problems, so it couldn't hurt to just pop a known good one in there for giggles. They're cheap and way too easy to change.

__________________
Streetside: 1987 Mercedes 300E Petrol Blue/Green
2014 Ford Mustang Grabber Blue
1999 Ford Ranger Green

Dockside: 1968 Eltro 17
1985 Silverton 34C

You are very simply not getting fuel. Don't bother changing anything until you figure out why gas is not getting to the cylinder. Bad ovp will make the car run terribly, but run.

First, disconnect an injector line from the injector. Bend it up slightly to get a small cup or something to catch fuel. Stick a screwdriver or something to deflect the air "plate" as low as you can. Turn the key up until you start, but don't start.

It should squirt out a piss-like consistincy of fuel. If it does, you have clogged injectors, if it does not, then you have to start going backwards.

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Eugene

10 E63 AMG
93 300te 4matic
07 BMW X3
14 Ford F-150 Fx2

I syphoned most of what was left of the old fuel and then a fair amount of ugly old gas drained when I changed the fuel filter. I put fresh fuel in prior to the first start attempt. I disconnected the fuel line prior to the fuel distribution system and there was pretty good pressure when the key was turned.

I disconnected the line at the injectors. The line was wet, but not streaming when the key was turned or starter engaged. My question is - is there a single input or valve that would prevent the fuel distribution system from allowing fuel to the injectors? I want to make sure there is no vacuum line or simple check this before I replace the fuel distro.

I appreciate y'all taking the time during the holidays to help with this.

Dan

Your original statement that this eliminates the fuel pump relay as the problem is wrong. If you give it a squirt of fuel (ether or whatever, something flammable) and it fires, it means you are not getting fuel, so you more than likely have a fuel pump issue, the pump itself or the relay. You can "jump" the relay easily and see if it runs, then you know.

MORE than likely NOT the OVP because the car WILL run without the OVP, just not very well.

For a car sitting a long time the pump may be seized, sometimes a tap with a hammer (on the electrical motor itself) will unstick it.

__________________
Click here to see the items I have up for auction at EBay

Click here to see a photo album of my '62 Sprite Project Moneypit (Now Sold)

There's another fuel filter just at the connection to the Fuel distributor.
Make sure this is not blocked.


If you pressurize the fuel system - turn the ignition key to on - then slightly loosen each injector line at the fuel distributor one by one - fuel should come out.

Next step would be to completely remove the Air mixture unit and clean it. Make sure that the plunger from the fuel distributor is not jammed up.

Make sure the air plate is not jammed up.

Not mentioned before, the air plate has to be down some or all the way before you will see fuel at the injectors. The plate should go down with some resistance and come back up freely (on it's own). If the valve in the fuel distributor is gummed up, it won't want to move down at all. DO NOT force it! Check for spray at the injectors with the pump relay jumpered and the air plate held down. Try to do this with the injector still hooked to it's fuel line. This will give an initial check of fuel pressure. It takes 70 lbs (I think) of pressure to open the injectors.
Edit, I'm sorry, I missed the post by Eugene about deflecting the air plate. Still, I recommend you remove the injector and check for fuel with it still hooked to the fuel distributor.

Good luck,
Paul

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84 500 SEL (307,xxx miles)

Thanks everyone. Okay the next question would be jumpering the relay. Which pin positions do I jump?

Dan

I think it is pins 7&8 in the fuel pump relay socket. The pins on the bottom of the relay are different. I would suggest you disconnect the negative battery terminal, install the jumper, have the injector ready to observe, push down air plate, touch battery cable to battery for a few seconds and see what happens. For this test, the ignition does not need to be on. Don't leave the jumper in and battery connected for a long time until we determine what the problem is. An internal leak could fill the engine with fuel.

Paul

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84 500 SEL (307,xxx miles)

I would just jump it and try starting it, or jump it and have someone listen to see if the pump is running or not, but it's "funner" to see if it starts.
I think those are the right socket numbers, they are directly across from each other and about in the middle (where the plastic pin is betwen the rows that makes sure you are putting the relay in the right way).
There is a diagram on top (or side) of the relay that shows the pin assignments, I believe there are #30 and #87 or 87s.
I always had access to a wire lead set which properly plugged in to the round sockets, you might have to come up with something a bit cruder, hopefully some insulated wire, otherwise if you go really crude like a wire clothes hangar, etc, make sure the bare wire doesn't touch anything metal, keep the wire really short, just long enough to do the job.

__________________
Click here to see the items I have up for auction at EBay

Click here to see a photo album of my '62 Sprite Project Moneypit (Now Sold)

Its sad and rather difficult to diagnose problems when people half read responses, or worse, have no good understanding of the system at question.

He said he can hear the pumps. He said he has fuel to the distributor, including pressure, its at the injectors he says he isnt seeing pressure.

Regardless. Any good manual would tell you to start with a fuel pump pressure and volume test.

And, I would remove all the injectors and have them tested. A clogged injector that only allows a small flow, will cause that cylinder run lean, and the O2 will call for more fuel to compensate, which could lead to burning down a cylinder, as well as the Cat. But resolve the other issues first so you dont feed gunk into your freshly tested injectors.

Ozarkdude, you are correct but this car won't start at all without adding fuel to the intake. If I had the car, there would have been a fuel pressure gauge on it just after checking for ignition. But my first guess is he doesn't have a fuel gauge that will work on these cars. I had rather see some simple LOW COST test done first rather than spending money on things that may not be needed. Then we can go on and fix/replace the necessary parts.

Just my $.02
Paul

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84 500 SEL (307,xxx miles)

You really do need a gauge and an FSM to check a lot of it.

Okay, after taking it all on board, here's where it stands...

I checked the filter at the fuel distribution unit and it was clean. I pulled the fuel pump relay and jumped the terminal. The pumps, or at least a pump was audibly running, but the car failed to start. I removed a line to one of the injectors and there was no pressure with the pumps running with the air plate depressed. I open the fuel line prior to the fuel distribution unit under the same conditions and the result was the same, no pressure. When I checked pressure there previously (before my first post) with the relay in place and turning the engine over there was some pressure. Not a fountain, but some, but now there is none.

I suspect, unless there is a severe blockage in the line between the filter and fuel distro unit, the pumps need replacing as the next step. If that doesn't do it, I'll be back for more.

I'll also see if I can find a fuel gauge to measure the pressure.
Dan