Hello, my 1985 244 DL started having difficulty starting when the engine is cold (i.e. started for the first time in a period of 8+ hours).

The car turns over as normal but doesn't fire as normal. No sputtering or anything, just normal cranking for about 10 to 15 seconds before starting which is suddenly abnormal. As a result the exhaust smells very rich when it first starts up.

Once engine warm, starts turn-key as normal.

Does anyone have any troubleshooting they would recommend for this issue? I have read in some other forums about the engine temp sensor mounted under the intake causing erratic issues but wasn't sure if my symptoms lined up with this.

Appreciate your input very much. Thank you

Hi,

A failed FPR diaphragm may reduce the gas line pressure, but it wont allow gas to drain back to the tank. That is the responsibility of a check valve which is screwed on to the outlet of the main fuel pump under your car. I think 15 seconds is longer than a primed pump needs to build pressure, so it may well be draining back.

I would pull a spark plug after 10 seconds of cranking. If it's dry, I'd suspect a fuel issue. If it's wet, the engine might need a tune up or be getting excess fuel from a failed FPR or engine temp sensor.

If you're smelling gas on start up, I'd look first at plugs, cap, rotor and wires. If any of these things are under performing, it's often the case that they'll start a warm engine but not a cold one.

Good luck
Peter

Hi Peter,

I agree with your whole first paragraph except for it does not drain the back to the tank.
The FPR is always sending excess gas from a running pump back to the tank.
That is how it maintains constant fuel rail pressure.
If that valve seat leaks bye, in a static mode, it too goes back to the tank via the return line.

Yes, the main pump has a check valve that only closes when the pump is off. It can be the sixth!
There are six or seven ways to lose rest pressure from the rail. Four injectors plus, if fitted, a cold start injector and then the FPR.
Despite the odds, the FPR seems to be the most common failure.

If it’s leaking bye it either loses rest pressure overnight or all the time on every start it will take a bit of time for it to refill the complete fuel line.
I also agree that the 10 cranking seconds is a terribly long time for the pump to fill it up full again with a check valve that’s working properly.
There is another caveat, if there is no in-tank pump working.
Add on, when the fuel tank is way less than half full and it will definitely make it worse.

In LH systems used a cold start injector up until about 1990 or so.
Removing it, helped pay for the EGR’s that became mandatory on some vehicles.
The LH 2.4 and 3.1 varies the cold start mixture with pluse width changes to the four injectors only.

It’s done by using information from the AMM, a coolant temperature sensor and then the O2 sensor until it warms up. The system goes into a “closed loop mode” when that happens.
Ahead of that, it was running on a preset cold start program in the ECU looking at the first two readings.

I hope this helps any and all reading our discussions.

Phil

Hi,

It’s just an off the top guess, but it sounds like you could be losing “at rest” fuel rail volume over that period of time. The fuel pump has to catch up to refill it would explain the sudden issue of cranking longer.
This could be most likely caused by a leaking down Fuel Pressure Regulator (FPR).
If you have never changed one out and it does not look nice and new It is an item that does have a failure rate that a little higher on these age cars.
It is located to the left of the throttle body and has two rubber lines connected to it. The bigger is a fuel return line to the fuel tank.

If the FPR has a tiny split in the vacuum diaphragm it will leak into the chamber above it.
If this happens, that gasoline in there gets sucked into the intake manifold through the smaller vacuum line over to the throttle body. The engine will run rough and rich for a short time.
Check it for gasoline or a strong smell in the vacuum line of it before starting the engine next time.
If it’s really bad some gasoline might even leak out the barbed nipple.

If you do not strike gasoline in there, at least suck on the hose to the FPR to see if it holds a vacuum. It should always hold a vacuum after you stick your tongue in the hose. This also checks that vacuum line for splits.
Try to refrain from using too much spit on your tongue! (:-) O (:-). It’s less tasty that way! (:)

A good FPR will not let gas leak back to the tank after shut down either.
There is a ball and seat that the diaphragm opens and closes against a spring to regulate a precise pressure.
When I’m in doubt about it leaking out I remove the return line and removed residual gas from that area.
I then put a piece of paper towel in the tip and cap the nipple with a piece plugged hose or plastic cap or electrical tape.
I then later check it to see if it became wet again after doing my setup.
If the tape is still not stuck, you might have your answer on that in?

Give it a try, you might like it for your issue.

Phil

Thank you for your responses! I will try troubleshooting with this collective information and see what turns up. Incidentally this morning it was 20 degreesF outside and the car started right up. Seems like the long cranking issue is in warmer temperatures (45 degrees and up).

Appreciate the help!