yorkee

I have a 84 944 and it has been reliable for last two years (knock wood). Couple days ago, I have issue starting it in the morning. It crank but won't start. Since I am rushing to work I just took another car. The 944 has been left outside in rain for couple of days. (Garage has been occupied by multiple projects)

I finally clear out the garage and push the 944 into the garage to look at it. I checked the spark plug to make sure they are good (I change time recently). Then I connect a fuel pressure tester on the fuel rail to make sure its pumping gas. I am able to start it after a few crank!

I really didn't do anything other than checking the spark and checking fuel pressure. Now I am a bit more concern... I will be less concern if I actually replaced a worn-out or defect parts. The crank-but-won't-start might be random. I am about to take a long trip with the 944 and I don't want to stranded in the middle of my trip. Any thought?

mel_t_vin

Unless you know what was not present during no-start [fuel, spark, compression], we would only be hazarding a guess.

In that case, random no-starts in a 944, in no particular order...

- cap/rotor [moisture due to rain]
- coil terminals [moisture due to rain]
- DME relay
- S/R sensors
- DME

PeteL

I would also add DME temp sensor (particularly the wiring). The last two no-starts I had were the wires in the boot of the connector shorting out.

yorkee

it was all good and normal and it happen again. this time it fail in a gas/service station and left me stranded. I check the cap rotor / terminals and it seems okay. That said it is hard to properly check in the rain. Both times I can start it again after I release the fuel rail screw.. Would there be water in my gas tank? or what other possibilities?

mel_t_vin

Don't know...did you happen to drive around, in the rain, with your filler door open and fuel cap off?


If, you are serious about determining the root cause of this/any issue, then, you need to be serious about documenting the conditions of the given failure mode [with details].

It could be many, many, things. Again, unless you know what was not present during no-start [fuel, spark, compression], we would only be hazarding a guess.

To own these cars, you really need to embrace trouble-shooting from a logical, systematic, perspective. If that's not for you, be prepared to spend $$$ paying someone else to do it for you. In that case, you'd probably be better [cheaper] off, in the long run, with a 2012 Hyundai or Kia.


Okay, I'll play...one more time. Doesn't sound like rain necessarily has anything to do with your issue. Hazarding a guess...sounds like your fuel pressure regulator is failing, spiking your fuel pressure, and preventing the car from running due to an overly rich condition. The situation is mitigated when you relieve fuel pressure in the rail by removing the nut [w/ spring and ball, correct?].

Disconnect the vacuum line at the FPR...do you see/smell any gas? If so, FPR is shot. Replace. Check vacuum line at the FPD, as well.

Next time this happens, disconnect the electrical connector from one of you injectors, leaving three connected. Try to start your car. Does it start, but idle poorly? If so, your FPR is shot. Replace.

42 yrs w/porsche

X2 on the pressure regulator and damper as Allen described. I saw this quite a few times where disabling one of the injectors will allow it to start. Side note: It's generally more of a problem when the engine is warmed up and can't tolerate the extra fuel that's being dumped into the intake.--Dave

athens944

Is your tach bouncing when you crank the engine? Reference sensors can sometimes cause random no starts

mel_t_vin

Dave, true what you said about a warm engine. In the OPs case, his no-start has occurred on both cold start and warm start. Maybe it's not the FPR/FPD...

mel_t_vin

True...both reference sensors, and/or their associated wiring/harnesses, have been found to be the root cause of many a no-start.

yorkee

Thanks everyone for the help.

It was all good for last couple months and it seems to act up again..

I was not in my own garage so I can only check basics. I checked and there is spark (at least the first cylinder). And When I crank there is fuel coming out from the fuel rail.

I also disable one of the first injector and try to start it, no luck.

Took out the vacuum hose from the FPR and there is no smell of gas.

I am going to bring the fuel gauge as well as compression tester to check the actual fuel pressure value and compression value next time...

When you guys mention tach bouncing, My tech is bouncing maybe the first 50rpm only. (within the yellow area of the 0 mark) I feel its more from the vibration of the car. How far the tech needle should bounce?

Thanks in advacne

yorkee

Just check interweb about the tech bounce and I consider mine bounce. So its not crank position sensor.

Tested all 4 spark plug and all of them has spark.

Hook up the fuel pressure gauge and I got a nice 35psi.

Also swap 2 DME relay with no luck.

Will test electronic when I have a chance.... Well, at least its consistence now

yorkee

So today I did compression test on all 4 cylinder, front to back:
120psi
135psi
110psi
135psi

I also swap out the 3 months old spark with the original spark plug that was on the car one by one as I compression test each cylinder. Guess what… The car start after replacing the last one!

So much for the premium spark plug… (NGK Iridium BPR5EIX)

I still wonder… I have those plug in the car for the last couple months and it works fine. They all gap correctly. Why they fail now? Shouldn't they fail couple months ago?

I also wonder if it make any difference if I put a bit of antiseize on the plugs before I install…. the anti-seize shield the plug from connecting to the engine body… thoughts?

Thanks for everyone who help me diagnose my problem, and those who push me to solve problem logically.

konakat

So it sounds like you have seen this with both cold and hot starts? Has the engine ever died while running, or is it just a start issue?

yorkee

both cold and hot starts. mostly cold start. The engine never die while running, but sometimes it stumble a little bit during acceleration, and pick up from low rpm as well.

mel_t_vin

Why stray from the beaten path...Bosch WR8D, copper or silver.

So, after swapping your plugs, has your cold/hot start issue been resolved?