pcm question

[crazymind]

If the pcm sees that under Hood temps are getting too high does it have the ability to turn the fuel pump off? I ask because my 99 4.0 dichotomy dies when the temperature climes into the 90's no other time

 

[waskly]

no

considering engine operating temps is around 200 degrees cats run at 1200 degree, 90 degree weather wont affect anything.

 

[crazymind]

I was reading up on so forums about vapor lock and stumbled across one. it was describing my situation almost perfect. what they were saying was that it was the ect (engine coolant temp) sensor, but to my dismay they didnt post anything anout it fixing it. would this be worth the effort to replace.

granted everything is pretty warm under there it only happens when it reaches the 90's ive never had it die anyother time, even in the 80's sounds wierd i know but the x i swear has a mind of her own

 

[2000StreetRod]

ECT sensor & fuel pump

The engine coolant temperature (ECT) sensor output significantly affects the air/fuel ratio as well as the idle speed. If the sensor output exceeds established limits the PCM will set a DTC. If your engine cold starts well and the idle speed decreases as the engine warms and runs smooth then your ECT sensor is probably functional.

There is a possibility that your fuel pump is weak and overheating. One member has this situation and temporarily solves it by adding cool fuel to the tank. The cool fuel cools the fuel pump increasing the fuel pressure. I suggest that you check your fuel pressure when the temperature is cool and then again when hot. Your 99 Explorer has a returnless fuel system and the pressure should always exceed 60 psi. Has it been more than 30,000 miles since you replaced your fuel filter? I suspect that clogged fuel filters shorten the life of fuel pumps.

 

[imp]

......... I suspect that clogged fuel filters shorten the life of fuel pumps..............

I do, too! This would be especially true for vehicles driven much of the time where engine load is high, such as high-speed driving, or towing. At idle speed, or relatively low engine loads, the pump consumes less energy overcoming the pressure dropped across the clogged/partially clogged filter, due to much less flow rate called for. The more energy the pump must produce, the hotter it will run, most likely lowering it's life expectancy.

imp

 

[crazymind]

both are just change the fuel filter and the screen on the pump both with barley a thousand mile on them. and i was at one point looking to put focred induction on it and i no longer have the retureless style. when its running im at about 56 to 62ish psi. all the fuel lines are wraped aswell to keep the heat outa them

 

[crazymind]

And when it dies there is bout 2 psi but I can still hear the pump turn on in tank

 

[2000StreetRod]

Return fuel system conversion?

How did you convert from the stock returnless fuel system to a return fuel system?

On the returnless system the fuel pressure regulator is in the tank with the pump and there is a pressure damper on the fuel rail. On a stock return type fuel system the fuel pressure regulator is on the fuel rail.

I suspect either your fuel pump or your pressure regulator is failing.

 

[crazymind]

When I had my tank out to put in the bigger fuel pump I took the regulator took the dampiner off put a custom adapter on ran to the regulated and ran a return line. All the stock stuff is gone but the line itself. And if I keep off the gas it'll spit and sputter fighting to run but as soon touch the peddle to see if I can keep it running she dies

 

[crazymind]

Bump

 

[2000StreetRod]

vacuum controlled pressure regulator?

Is your fuel pressure regulator vacuum controlled? If so, then the fuel pressure should be maximum when the vacuum hose is disconnected and plugged and minimum at idle and maximum vacuum. If the pump is running and you only have 2 psi then the regulator could be defective. You can test it with a hand vacuum pump.

Another possibility is that your high flow pump is overloading the electrical supply. What is the specified current draw for your high flow pump? You can pull the fuel pump relay in the battery junction box and insert a jumper between pins 3 and 5. Then the fuel pump should run continuously. If the pressure stays high then maybe your fuel pump relay is failing. I believe you can swap the fuel pump relay with either the horn, rear wiper down or rear wiper up relays.

Even if your high flow fuel pump is fairly new that doesn't mean it isn't bad. Especially if you bought an inexpensive you via eBay. Several members have complained about some of the junk fuel pumps they purchased on eBay.

 

[crazymind]

If its over loading the system would it be possible to run all new wire? Its passed my mind a few time but I've never blown a fuse and its still the stock thirty amp. Also it did it with the inursu switch so I put a manual switch in rated for 30 amps but it still cuts out. Could it be possible its vapor locking? If so could the ect be faulty at higher temps? Cuzco when I pop the Hood to check fuel pressure under Hood temps feel a bit hotter than normal.

 

[2000StreetRod]

Inertia switch?

If you have defeated the inertia switch please do not drive your vehicle. It is unsafe for you and anyone else in or near your vehicle if you have an accident.

The PCM only allows the fuel pump relay to close for a few seconds unless the PCM senses the engine is rotating as sensed by the crankshaft position sensor. When the key is first switched to Run the fuel pressure should rise above 60 psi and stay there for several minutes even though the pump is no longer running. If it drops rapidly then the fuel pressure regulator is defective or installed incorrectly.

The PCM monitors the voltage from the fuel pump relay to the inertia switch for diagnostic purposes. That allows it to determine if the fuel pump relay is not closing.

I can't think of any way that an incorrect ECT would prompt the PCM to disable the fuel pump. It might limit engine rpm via the fuel injectors or ignition.

 

[crazymind]

last time i had the tank out i pried the system to make sure i had no leaks and it stayed there for a good half hour. There is no cel or the fuel light on the dash either

 

[crazymind]

I should've also said after bout ten 15 minutes it'll start back up but shell only go for about a mile than die again. If I have to get anywere I have to wait till the temp drops to the 80's and no problem at all

 

[budwich]

IF your problem is as reproducible as you describe, get a meter on some of the wiring and find what you are chasing, then you are likely to find your issue which is likely a poor connection / splice that doesn't like the "kitchen" when its hot.

 

[crazymind]

Should I do it on the fuel pump since when it does happen I only at 2 psi?

 

[budwich]

you need to check to "whole" circuit to find out what electrical conditions exist at the time of "momentary death"... then you will likely have an "easy fix" as opposed to guessing at what the issue is and throwing parts and time at "ghosts".

 

[crazymind]

do you think that if i do an ohm check that itll work or wait till i have the problem to do it than?

 

[budwich]

may but you are more likely to find your issue (and the solution) IF the problem is there. Right now you don't know if you have a voltage problem, ground problem, continuity problem / resistance issue so you are just "shooting in the dark".