fuel pump won't energize

[jascolt]

hello all, this si my first post so thanks in advance.

I have a 96 ford explorer with the v6 engine and it has trouble starting. When you turn the key on the fuel pump does not always come on (you can hear the pump come on just before cranking) and when it doesnt, the car won't crank. Sometimes the pump does come on and it cranks fine. I took it to a mechanic and he replaced MAS but the prob was not fixed. I took it back and he kept it for a couple of weeks and replaced fuel pump and the problem still persisted. He could not find out what else to do. When you crank it, it tries to crank but just won't ever turn over unless the fuel pump engaged before starting. I replaced fuel pump relay without results.

The car has 220k miles on it but is still a usable vehicle if I can get it to starting normally. Any suggestions?

 

[Wrench]

Std. or Automatic? The fuel pump prompt on startup has nothing to do with a no crank issue. Clutch/park switch! What is the fuel pump pressure at cold start (KOEO) and does it hold pressure after prompt.

 

[BrooklynBay]

Welcome to this forum! Cranking the starter is not related to the fuel pump in any way unless there is some sort of alarm system cutting out both of them at the same time.

 

[skoal_mint]

does your head lights or anything come on when this problem happens? maybe your ignition switch is going on your, or wires to it

 

[jascolt]

All lights are fine and new battery. Its just that when the key is turned to on the fuel pump doesnt make its whirring noise and car won't start. But every once in a while it does make the whirring noise and the car will start. The whirring noise I am referring to is when the fuel pump runs for 2-3 seconds when key is turned to on.
I guess what I need to know is what could prevent the fuel pump from running for the 2-3 seconds pre-start? I replaced relays and fuel cut-off switch is not activated. Also this prob use to be every once in a while, then more frequent and it went to mechanic, and has now progressed so that it doesn't start more than it starts.
Its automatic.

 

[BrooklynBay]

You said that the fuel pump relay was replaced, but what about the PCM relay? Do you get a check engine light when you turn the key to the accessory position when you don't hear the fuel pump priming?

 

[jascolt]

I havn't replaced the pcm relay but I swapped it arround with the abs relay. Also when it does crank everything works fine, wouldn't this mean that the pcm relay is fine or not?

I do not get a check engine light but its possible it burned out many miles ago because of O2 sensors that were replaced and the light would be reset by dealer but would come back on in a few days. They said there was nothing wrong with the car at that time so the light remained on and may have burned out. This happenned arround 100k miles.

 

[Cobraguy]

The fuel pump relay and the no crank condition ARE related in this case guys! If he doesn't get the pump to energize, it won't crank! So, there is definitely a relation. Now the hard part is finding it since they don't APPEAR to be related anywhere. This sounds like a bad and intermittent ground. This one could be tough to find. The alarm suggestion is a good one.

For God's sake, get a new mechanic. Those are ridiculous conclusions for your symptoms.

 

[jascolt]

before I go changing all these parts I would like to know all of your opinions on whether this could be aresult of the dpfe sensor, the egr valve itself, crankshaft position sensor, fuel pump regulator, or camshaft position sensor?
Would either of these by itself prohibit the pump from priming upon start-up?
If so that would give me a starting point.

Anyway to check on the alarm suggestion?

In defense of the mechanic, he couldnt get it to do it all the time he had it, it seemed to start fine with him and I had suggessted it could be fuel pump the first time I took it to him and he said he didnt think it was the pump and kept it for 2 weeks with no trouble after installing maf sensor. I was dissatisfied when I got it back because it had same prob and I had just paid him $230 and still felt it was the fuel pump so I told him so. He talked my wife into bringing the car in again and he kept it another 2 weeks and could not replicate the prob but put in a new fuel pump for free anyway and still didnt fix the prob. He really is a good cert. mechanic who has worked on my cars for years and I have sent him a lot business. He said he was at a loss for what may be wrong I think he really tried his best. But...................

 

[Wrench]

ok- to start over again you need an electrical schematic of your year and model for the start and fuel circuit. With your mileage I think you need a new fuel pump but a pressure check will confirm this. Do you have an alarm system or an immoblizer no start system?

 

[jascolt]

I have elec. schematic from my haynes book and it makes very small refrence to the pats(passive anti theft system) on the schematic but does not mention it anywhere else in the book. I don't think mine has the pats, only the alarm that is on most cars that you can set off with your key fob or an earthquake. The car does have a new fuel pump.

Yestersday I worked on the car for a few hours and could not make it malfunction. The pump primed and the car started every time, this after having not started for about a month on random attempts. I unhooked dpfe sensor, egr, iac, maf all one at a time and none of them prevented pump from priming. I totally dissassembled power distribution box and made sure all the relay prongs were making good contact. I drove the car arround to get the temp up then let it set a while. None of these actions caused the pump not to prime and the car to start. If it ever does not start, it seems there is nothing you can do to make it no matter how long you wait.

If anyone knows the answer, dont be shy. I know someone out there is laughing to themselves thinking "poor sucker, I been there before".

 

[Wrench]

No I don't think any body is laughing at your problem. Do you have two key fobs? Use the one with no extra keys on it for awhile to prove your original key is ok. Technically you should have three ignition keys programed to your computer if you have the immobolizer factory system.
Forget the Haynes book and get the factory wiring diagrams as Haynes is too broad and out dated. You should never stab a wire insulation but back prob at junction points to prove power or gnd exist.

 

[#1stunta]

does anybody know what and where these wires that deal with this problem. i had a red and black wire the go to the anti theft come out the the under hood fuse pannel and now i have fuel problems. pretty sure that this is the problem with the fuel cut off thing with the anti theft but i can t find a diagram to see were these wires go.

 

[BrianDye]

When the pump doesnt engage does the engine actually not even crank? Or does it crank, but just not start?

If it doesnt crank when the pump doesnt come on, I would be willing to bet money it was something todo with an alarm...

 

[#1stunta]

no it actually starts. when i put a scanner on it and do the live scan the scanner reads CL_fault in fuel system but no check engine or fault codes. what lead me to believe it had something to do with the alarm is while checking for another short with the ignition on, i found a red and a black wire from the alarm box that went through the fire wall an into the main fuse box. the wire was loose or just about loose when i found, i first i thought that it might have been to a vibration sensing unit that was no longer there, so i just wrapped it up under the dash and went to the auto parts store for a part when i came out and started my truck (used the alarm to lock and unlock doors ect. turn off the little flashing light as usual to start the truck ) and that's when the problem started. i barley made it a mile home limping and bogging out the whole way. its hasn't run good for any longer then 2 minutes since. i dont have a fuel pressure gauge but i changed the fuel filter today there was really no pressure in the line when i disconnected the filter which i thought was the problem. i checked at the fuel rail buy just pushing in the valve where you would hook the pressure gauge to and gas did not squirt out. it gave a little squirt ( didn't make it passed the valve cover) and then dribbled the rest out. (what you might expect if there was just some fuel in the line.) it seems like it builds a little pressure if it sits long enough or if i turn the ignition on and off enough times while checking other things out to start up and run for a minute but after it just chugs and stalls out. i think that some how the pump pumps when you turn the ignition on at first and that is how it builds up a little pressure while i am tinkering trying to track down the short in the 26 circuit ( reverse lights switch found it.)

 

[#1stunta]

the starter and the fuel thing are on different loops of the alarm. the starter one is still hooked up. i only have a haynes manual so the wiring is really vauge