I had an intermittent hot start problem that has slowly developed into a real nuisance. After replacing the fuel pump check valve, pulling the vacuum lines on the fuel pressure regulator and dampers and checking them for fuel smell, and checking the cold and hot ohm readings on both temp II sensor leads, I ordered a fuel pressure gauge from Roger (928srus.com) to test the fuel pressure. The fuel pressure remains a steady 29psi when idling, then goes up into the 30's after the car is shut off, which is normal I think. If I immediately try to restart the car, it starts fine, but the longer I wait to restart, the more difficult it is to start. After a few minutes, it won't start at all. After about an hour, it starts right up. The fuel pressure gauge shows around 10-15psi after shutting off the car and letting it sit for 15 minutes. Can I assume that the loss of pressure, and the hot start problem, is from a fuel injector leak? There are no visible leaks or gas smell anywhere.

If it is a fuel injector leak, would it be best to go ahead and purchase a new set of Ford injectors for $200 and be done with it, or pay to have the old ones serviced? Would the leaky ones need to be replaced anyway?

Thanks!

 

Sounds like classic leaky injector symptoms - though I would have thought it needed more than 1 hour for exess fuel flooding cylinders to vaporize.

I don't think cleaning fixes a leak problem. I bought set of the Fords and she starts first time, every time ever since.

 

I would tend to agree with StratfordShark. It restarts immediately OK, before the leaky injectors have had a chance to flood the cylinders, but fails after the injectors have had more time to leak, then starts OK much later after the gas has evaporated = "classic leaky injector symptoms." However, I agree it should take longer for the gas to evaporate. I had a car that did this and it took at least 4-6 hours before it would start normally. Any earlier than that (other than immediately) and I could only get it to start after a lot of wideopen throttle cranking, and it would sputter quite a bit initially as it cleared the gas.

Your fuel pressure observations are OK for an 86, although it should hold one bar for 20 minutes after shutdown. I would expect with a leak that it would fall even faster than you observe.

Although it's possible cleaning MAY resolve the leaks, the new Fords at $200 would be the best bet.

 

I wouldn't blame the injectors. My '85 has new injectors and does this from time to time. Press the pedal all the way to the floor and see if it will start the next time it happens. If it does, problem solved.

 

I assume you have tried starting with foot to the floor ?

When it won't start, have you checked there is spark, and that fuel pump runs when engine is cranked ?

 

I've tried the WOT trick several times, but it didn't make a difference. The fuel pump runs when the engine is cranked, but I haven't checked for spark. I figured since it immediately restarts after shut down, that it is getting spark. The crank speed sensor was the second-to-last thing on my list to check; the LH was last....hopefully, it doesn't go that far.

I went ahead and ordered the Ford injectors from here: http://www.blueovalindustries.com/pr...p?pid=99013344
They were $209 with shipping for a full set. I'll post results after the injectors are in.

Thanks for the guidance everyone!

 

Man, that is a great deal on the injectors. If you are running on original injectors, this is a good move even if it is not the cause of your starting problem.

 

Given the steps you have tried I would not assume that you have spark. The hot soak back problem that generally is seen in fuel systems can also happen in electrical systems. Given that it is repeatable, next time it will not start throw a timing light on to check for spark.

Given the fuel pressure decay that you reported I don't suspect that injector leakage is the issue which also seems to be confirmed by the lack of full throttle helping to clear it to start.

 

Tangent momentary diversion-- (not the same as a hijack since you are still in control....)

Are the 19# versions shown at http://www.blueovalindustries.com/products.php?pid=572 the correct ones for my 1989 S4? If so, a set will be on the way to go in during the upcoming fall intake refresh project. This is a smoking deal if they are the correct part! Or is there a better option?


Diversion over, back to no-start discussion.

 

Dr. Bob: Those are correct. Summit Racing has them for $219.

 

Thanks, Bill. New parts are on the way. Now I'll need the o-rings. e-mail to Roger...

 

The injectors arrived super fast and were well packed. After installing them, the car fired right up and I immediately noticed that the idle was more smooth than before . The front wheels are off at the moment, so I can't drive it yet, but I did let it run until it was up to temp and then did several hot starts without experiencing any problem or hesitation. The fuel pressure didn't drop either. Hopefully this is a done deal and it is fixed......gotta take it for a cruise first to be sure.

 

EXCELLENT!

 

Did the new injectors fix the no hot start problem? Did you need to purchase "O" rings separately for the fuel injectors?

 

Answered:
More:
The Ford injectors need to have the correct o-rings swapped on to fit the 928 manifold openings. Roger has the o-rings, as well as the aftermarket injectors. Bluovalracing no longer offers the smokin' deal on the Mustang 19#/hr injectors, in fact doesn't carry them at al any more. My car loves these injectors, with significantly improved NOx readings. Speculating that mine were a little clogged, so a good cleaning should bring them back to new pwerformance. I'm not so sure that cleaning is a guaranteed cure for the leaking injector problem that jkelly solved with new.

Post your results please.