Starts and dies
 

Hi,

I moved my car outside of my garage and turned it off. When I went to start it again to move it back it started for about 1-2 seconds and quit. I tried again and this is all it would do. I disconnected the battery and retried. It started for about 5 seconds then quit. After leaving it overnight it started for about 8 seconds (Iwas about to put it in gear) then quit. Back to the 1 second thing... If I keep cranking I can crank thru the short period it runs (doesn't rev fast enough to kick out the bendix)then crank forever with no more fire. I can't even get it into my garage to work on it.

I looked in my "owner's bible" and tech manual for a reference to an oil sensor cut out switch but I couldn't find anything. Am I looking in the wrong place?

The car is a 1990 300TE 4matic with ProStart command start. When I try to start with the remote it barely cranks for 1-2 seconds then stops.

Anyone have any suggestions? Where is the oil pressure sensor cut-out (if it exists)?

Thanks.

Norm

RE: Starts and dies
 

Sounds like a fuel problem? See if you can hear the fuel pump running we cranking if not this could be a faulty fuel pump relay.
Hope this helps Lozza

RE: Starts and dies
 

I agree sounds like oil pressure switch which needs to sense oil pressure to keep fuel pump running after cranking stops.

I would place a multimeter across the pump terminals and ensure that voltage is present at the different stages of the start routine.
i.e. Ign on, crank and running.
An alternative way of doing this is to measure the injector rail fuel pressure. Some models have a schraeder valve on them for doing this.

JFI I don't think that your starter will have a bendix on it but more likely a solenoid engagement design (pre-engage).

Stuart

RE: Starts and dies
 

Hi,

I am on the road until Thursday so I won't be able to get to try any suggestions until then but I will consider all. The oil pressure cutout thing seems reasonable but I can't find a reference to it, yet. I won't be able to check my Hayne's manuals or CD service manual until the weekend.

Thanks for your suggestions.

Norm

RE: Starts and dies
 

Hi,

Here is where it stands...

I replaced the fuel filter as it was pretty plugged up but that didn't solve the problem. The pump only runs for less than half a second when the key is initially turned on, then it won't run AT ALL afterwards. I backed off the gas line connector to see if it was somehow pressuring up and shutting off but all I got was a small shot of gas while it ran then it shut off.

I Understand from my manuals that it should run during cranking and after the engine starts but that isn't happening.

I can't find any reference to a signal that stops the pump from running after turning on the key but that it what it seems to be doing so I guess I will be ordering a new MAS fuel pump relay.

Am I on the right track?

Thanks

RE: Starts and dies
 

Hi,

Not familiar with 1990 ProStart command start.

However as I stated previously you are on the right track.

Power is supplied to the fuel pump through several different circuits.

When the ignition is first turned on some systems allow the pump to run for a given period of time before cutting off. This time period is set to ensure that there is sufficient time for the cranking procedure to be completed. This is controlled by the starting procedure "module". I suspect that ProStart is of this type.

The engine is then cranked and once running engine oil pressure triggers a relay which supplies power to the fuel pump. These relays / oil pressure switch can give problems.

Other methods of supplying power are used and include inertia switches to detect and cut of supply if a crash occurs.

I guess you have already had a multimeter across the pump terminals. If so you need to determine what is controlling the cranking phase supply.

Stuart

RE: Starts and dies
 

Thanks for the reply, Stuart.

I don't actually think it is 'remote start' related. As I mentioned, the pump does run, but it stops after only a half second or so. My manual states it should run for about a second when the key is turned on. Now that I have drained the fuel lines and filter (after changing the filter) it doesn't start at all. I guess it started before for only a few seconds because the fuel accumulator held enough pressure that when the pump ran it provided enough fuel to fire the engine.

I have ordered a MAS fuel pump relay and hope it arrives by the time I return from the north (I will be away on an inspection trip to a northern airport in Canada's NWT until Friday).

I don't like playing the 'pull and replace game' when it comes to fixing cars but these cars are so darn complicated it seems this is the only way to do it, or take it to an MB dealer and the closest one to me is almost 30 miles away. My local GM guys won't touch it for this kind of problem. Oh well...

I will post my findings as they occur.

Norm

RE: Starts and dies
 

Aaah.

So ProStart is Remote Start. Unlikely to be that.

Yes system often holds residual pressure.

Key is whether there is power at the pump prior to, and after cranking. Simple multimeter job to check out.

There is a relay in the circuit. Could be that but not convinced. Anyway low cost to swap out. I usually swap with one of the other existing similar relays.

If you NOW say the pump isn't running with ignition ON you need to determine whether it is a jammed pump or lack of power. i have seen jammed (rust/corrosion) between stator and rotor within the pump before but lack of power is more likely.

Should all be straightforward to resolve subject to multimeter test.

Stuart

Final solution to this problem (and I should have "seen" it before) was the OTHER fuel pump. Unfortunately, lying on my back under the car allowed only for seeing the pump in the rocker panel position. Since my manuals are sorely lacking on specific refences to the "estate" version of the car I was unaware that the second fuel pump was NOT part of the bunch of parts behind the panel. I thought maybe MB in their greater wisdom used a bigger/higher volume single pump so they could move the filter to where the second pump should have been. I didn't look for the second pump up by the fuel tank.

I will say no more...