Cranks too long when hot??

[daddystang]

I've got a problem that got me stumped. When I start the car up in the morning in cranks for about 2 seconds and starts right up. When I drive it around and it gets up to temperature 180*, and I come to a stop, turn it off, let it sit for a few minutes. Then try to start it again most of the time it can crank for about 10 seconds before it starts. When it does start it tends to stumble slightly until I hit the gas. I just replaced the distributor and TFI module with no luck at all. I'm starting to think it is a fuel problem, because it cranks strong, but stumbles until the gas is pressed.

Question: When you turn the key to on. Should I have fuel pressure on my guage at the schrader valve? Mine reads zero until I start cranking it. Then it bounces around until the car starts then it goes pretty steady to the setting that I set it to.

Any help you can provide would be greatly appreciated.

Joe

 

[HISSIN50]

You should build pressure during the prime-out but to check that, you have to let the key rest in the Run position for 3-5 seconds before trying to crank.

Any codes?

Have you checked your ECT calibration? I'd do it with a room temp sensor and then with the sensor at operating temps.

Because it only happens when hot and it figures itself out once it runs for some time, it's probably a sensory input issue.

Good luck.

 

[daddystang]

Thanks Hissin.

So I should see a reading on my fuel pressure guage if I turn the key to on for 3-5 seconds? I don't, it stays at zero until it starts.

I haven't pulled the codes in the past few months, but I will tomorrow after I drive it around for a while.

I replaced the ect last summer when it was doing the same thing last summer.

Thanks for any further input you may have.

Joe

 

[HISSIN50]

When you turn the key on, the pump should be able to build 30+ PSI during the prime-out. If it doesnt quite make it, once you crank the engine, the PIP tells the EEC to make the pump run and it builds more pressure.

If you dont have any pressure build from the prime-out, something is wrong.

I'd still check your ECT (since it takes 10 seconds to do - even if you just check it when it's hot and compare it to the list that JRichker put in the idle-surge sticky).

I've seen a similar issue arise because the sensors were heatsoaking so badly that the EEC didnt know what to initially think. Once coolant flowed for about 10-20 seconds and the sensor started getting real-time readings from non-stagnant coolant, the issue abated. I've found this by testing the sensors after a heat soak but before starting the car.

Good luck.

 

[daddystang]

Just so that I'm sure of the ECT, where exactly is it located? Is it on the metal coolant tubes? Just want to make sure we are talking about the same part.

I'm still unsure as to why I'm not building pressure with the key in the run position. Thanks for your continued input Hissin..

Joe

 

[HISSIN50]

The ECT is indeed on the passenger side coolant rail. It has a couple wires going to it.

Try cycling your key a few times before ever trying to crank the car. If you dont build any pressure that way, be sure the pump is priming at all in the first place.

 

[daddystang]

I'm pretty sure the pump is priming. When I turn the key to run I hear the pump. I will try cycling the key a few times today and see if it builds pressure at the guage. Could my guage be faulty?

I'll let you know. Thanks again.

 

[daddystang]

I pulled the codes and heres what I got.

With the key on engine running I got code 11 system pass.

With key on engine off I got code 15 Failure in Electronic Control Assembly ECA problems with keep alive memory. Can this be caused by the SCT chip and tune, or is the a problem with my computer? Any help as always is greatly appreciated. Thanks.

Oh, and all the tests were done several times at 180*.

 

[jrichker]

Code 15 - No Keep Alive Memory power to PCM pin 1 or bad PCM (Memory Test
Failure). The voltage to the Keep Alive Memory (KAM) is missing (wiring problem)
or the KAM is bad. The KAM holds all of the settings that the computer "learns" as
it operates and all the stored error codes that are generated as a result of
something malfunctioning while the engine is running. Use a voltmeter to check
the voltage to the pin 1 on the computer - you should always have 12 volts. No
constant 12 volts = bad wiring. If you do always have the 12 volts, then the KAM is
bad and the computer is faulty.

If the computer has to "relearn" all the optimum settings every time it powers up,
the initial 5-30 minutes of operation may exhibit surges, poor low speed performance,
and rough idle.

Note that some aftermarket chips will cause code 15 to set. Remove the chip,
clear the codes and retest.

Before replacing the computer, remove the battery ground cable for about 20
minutes. This will clear all the codes. Retest after several days of running. If the 15
code is gone, then don't worry about it. If it is still there, then you get to do some
troubleshooting.

Wiring diagrams for the proper model years are next…

For 86 models see http://www.autozone.com/images/cds/gif/large/0900823d80167158.gif

For 87 models see http://www.autozone.com/images/cds/gif/large/0900823d8016715e.gif

For 88 models see http://www.autozone.com/images/cds/gif/large/0900823d80167162.gif

For 89-90 models see http://www.autozone.com/images/cds/gif/large/0900823d8019595f.gif

For 91-93 models see http://www.autozone.com/images/cds/gif/large/0900823d80195960.gif

See the following website for some help from Tmoss (diagram designer) & Stang&2
Birds (website host) for help on 88-95 wiring Mustang FAQ - Engine Information

Diagram courtesy of Tmoss & Stang&2birds

http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

 

[daddystang]

Well I reset the codes and set my SCT chip to the stock setting program, and rescanned for codes. This time I got an 11 system pass with the key on engine off. So it seems that maybe the chip program was causing the code 15.

I'm going to check the ECT voltage reading tomorrow. I need to track down why my fuel pressure guage reads zero when the pump primes.

Thanks guys for the continued assistance.

If anyone has any thoughts about the FP guage please chime in.

 

[HISSIN50]

If your FP gauge works normal once the car is running, personally I'd be inclined to think that it's doing ok.

If you have a diagnostic or spare gauge, you could use it for comparison's sake.

If the check valve in the pump assembly gets weak, it can take multiple priming or extended cranking for the pump to build pressure. That's why the multiple primes before cranking test can sometimes be helpful.

Also, pumps will start showing weakness when they get hot. After you shut it off, the pump can heat-soak a bit (the returning fuel to the tank helps cool it during operation).

Good luck.

 

[daddystang]

Thanks for the reply...

I was talking to a car guy hear at work, and he said it sounded like a fuel pump issue to him also. That's a bummer as it's a 1 year old BBK 255lph pump. Is there a test I can do to prove that the pump is bad before I go dropping the tank, or is the fact that I get zero pounds at priming test enough?
If and when I do replace it, which pump do you guys suggest. I forget which brand was in my other Mustang, but I never had a problem with it.

Thanks for any further input. It's very appreciated.