1987 Mercury Marquis Flooding Out ( sometimes)

I’ve been working on my own vehicles for over 30 years and always do my own repairs.

I have an 89 Mustang GT, 59 T-bird and 74 Nova.

My friend has an 87 Marquis with the 5.0

( 105K )and here is the problem.

You shut the car off after its hot and get a no start condition.

He called me today and I went out to help him. I checked for spark with an extra spark plug and had a good strong blue spark.

I shot some starting fluid into the throttle body which had no effect, not even an attempt to start.

Held the gas pedal to the floor to shut off the injectors and after about 10-15 seconds of cranking she started to fire and sounded like it was running on 3 or 4 cylinders for about 15 seconds until the other cylinders cleared out with black smoke out the exhaust.

After that it ran smooth to my home and we shut it off for 30 seconds and the same thing, no start unless you kept it at WOT.

We repeated this process about 4 times, waiting anywhere from 30 seconds to 5 minutes.

I first thought a bad fuel pressure regulator so pulled the vac line off and nothing ( no fuel leaking )

I have worked on this car, putting in a new fuel pump and filter, leaky PS Pump, spark plugs ( tune up etc ).

The fuel pump does run going into the start position.

I have checked the EGR, cleaned the IAC and throttle body way before this problem started.

After a few repeats of this problem today in my drive way we now can’t get the car to

act up. Runs smooth as silk and restarts normally.

It does not do it every time and I’m here now scratching my head as it also happened about a week ago.

It has the same symptoms as a carbureted engine would do if severely flooded.

Any suggestions ?

Well, it would probably be a PITA but what I would be thinking about next is pulling the fuel rail and checking for injector leak down.

What type of injection? TBI or multi-port?

Its multi-port, what I don’t understand is, would all the injectors be bad to flood it out ? even if 4 were leaking the engine would at least attempt to start ? I want to hook up a fuel pressure gauge and see what happens after its shuts down. It got dark so could not do more and could not get the car to flood out again.

Drove it another 10 miles ( with someone following me ) and then back home and no symptoms, just does it when it wants to, sometimes several times a day then nothing for a week, but when it does flood out it will repeat itself then suddenly stop.

After the cylinders clear and running, its smooth as silk with steady idle and
no CEL.

It sounds like ALL the injectors are getting an open signal even though the ignition is off, allowing fuel to flood the engine…A bad ECM?? Also , when the key is turned off, that should kill the fuel pump. I do not know if the fuel system has a pressure bleed-off other than the injectors leaking, but I suspect it must. With zero fuel pressure, there should not be enough injector leakage to flood the engine. I’m not a fuel injection expert, so don’t take any of this as gospel, just things to check out. A long-shot would be the EVAP-canister system allowing fuel tank vapors to pour into the intake manifold in an uncontrolled manner, flooding the engine…

possably a bad ect(eng coolant temp sensor) for the pcm reading coolder eng temp causing rich fuel mixture at start up flooding the eng.

Just to throw something out there for consideration.
When you checked for a spark could it be that a spark is not present all of the time? You sprayed starting fluid into the intake with no results so maybe what you have is an erratic spark.

The black smoke could simply be gas pooling due to no spark and not necessarily an indicator of flooding due to a fuel system problem.

The 87 is one of those TFI-IV vehicles which are prone to ignition module problems and if the module has never failed then it’s a miracle.
Another possible cause of an erratic or no spark could be the electrical part of the ignition switch.

Sometimes the electrical part of the switches fail due to of all things, a dragging blower motor. The blower motor current passes directly through the switch instead of a relay and over time the high current draw of the blower (especially true of a worn blower or a blower running on the HIGH position a lot) can cause the switch to melt internally.

JMHO anyway and hope it helps.

I ended up taking the vehicle to my friends shop and he had the car for a few days.
Turns out the problem was the coolant temp sensor which would go whacko at times.

He had all his diagnostic equipment hooked up and found that the temp sensor would sometimes show that the coolant temp was at 40 degrees below zero causing the injectors to dump excessive fuel into the engine. A big temp difference when the outside temp here in FL is around 80 this time of year.

It also was throwing the MAF sensor into thinking that the vehicle was at a minus 2000 feet below sea level.

Just thought I would post an update as very few ever let us know what the oucome was after getting advise from this board.