fuel issue
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Junior User
Joined: Feb 2009
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From: Bartlett,ill
fuel issue
i have a 88 250 4x4 5.8l 351 when i turn the key to start the fuel pumps are not engaging and also in the on position there is no check engine light on usually it comes on b4 u start the truck it cranks but its not getting fuel any ideas would be helpful thank u doug
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Joined: Dec 2002
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Could be the switch that kills the fuel pump on an accident but I would think the CEL would still work if that was the problem. It could be a bad ground but more likely the fuse either to the fuel system or to the computer. Of course it could also be the computer - I think it is called the PCM on my '92 F150. If you want to see if the relay actually works you can use an ohmmeter to check the resistance across the coil which I would expect to be between10 and 30 ohms. You can pop the relay open to check for burned contacts and check for resistance across the contacts by maunally moving the mechanism. You could also use jumper wires and battery voltage to try activating the relay - listen for the click. You have to get correct polarity applied across the coil so if it didn't work the first time try switching the power connections. Sometimes you ahve more than one relay with the same part number on a vehicle so just swap the relays and see if the problem moves - that is what I would try before I even put my ohmmeter on a relay.
Tuned
Joined: Mar 2009
Posts: 373
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From: Ohio
if your check engine light isnt on your PCM relay is most likely in need of replacement. Ground pin #6 on your test connector and turn your key to on. If your fuel pump doesn't start cranking, check your inertia switch. If it's not up, your fuel pump is either dead or your wiring is messed up.
Tuned
Joined: Mar 2009
Posts: 373
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From: Ohio
most likely not. it sounds like you have a dead fuel pump. if the inertia switch is pressed down and the fuel pump isn't cranking when you ground pin 6 with the key in the on position, you need to start checking the wiring. get a test light and start with the wires at the fuel pump. if the light turns on you have a bad fuel pump, if not, trace the problem and do some rewiring. Does the Check Engine Light come on when you turn the key to the on position? If it doesn't your PCM could be bad, but it's most likely just the relay. Grounding pin 6 bypasses the PCM though so it's sounding like your fuel pumps dead
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From: Bartlett,ill
my inertia switch has a red button lookin thing on it and it looks like its pushed down but i dont know what its supposed to look like good or bad? when i grounded pin # 6 with key in the on position fuel pump did not turn on. when key is in the on position the check engine light is NOT on all that comes on is rabs light and a red battery light i just replaced battery and both relays on drivers side fender what is the PCM? power controle module?where is it located also i disconnected the terminals to the fuel pump and ran a direct wire from the battery to the pump and it turns on so maybe its not the pump? at this point im all out of ideas thanks for the help Doug
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Tuned
Joined: Mar 2009
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From: Ohio
your powertrain control module or PCM either has a bad relay or is bad. The inertia switch is fine being pushed down. Why the fuel pump didnt crank with pin 6 grounded is beyond me. did you at least hear the relay click?
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Thread Starter
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Junior User
Joined: Feb 2009
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From: Bartlett,ill
no the relay didnt even click and i would figure 2 that the fuel pump would kick on when grounded 2 pin6 wtf i am goin nuts its my dd and i need this thing goin asap thanks though where is the pcm located?
Postmaster
Joined: Oct 2003
Posts: 4,516
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From: SoCal
I have the factory wiring diagrams for all my Fords, but i dont have an 88 F-250 so cant give you exact info.
But heres how these normally work.
Turn the key to run & 12 volts from the ignition switch flows thru the coil side of the main relay.
The main relay closes & sends 12 volts thru the coil side of the pump relay & the PCM grounds this voltage to close the relay & send 12 volts to the pumps.
Since the CEL is not coming on & the pumps are not running you need to check for voltage from the ignition switch at the main relay.
BTW the the PCM is also not receiving voltage from the main relay which is why your CEL is not coming on.
But heres how these normally work.
Turn the key to run & 12 volts from the ignition switch flows thru the coil side of the main relay.
The main relay closes & sends 12 volts thru the coil side of the pump relay & the PCM grounds this voltage to close the relay & send 12 volts to the pumps.
Since the CEL is not coming on & the pumps are not running you need to check for voltage from the ignition switch at the main relay.
BTW the the PCM is also not receiving voltage from the main relay which is why your CEL is not coming on.
Postmaster
Joined: Oct 2003
Posts: 4,516
Likes: 1
From: SoCal
Like I said I dont have wiring diagrams for an 88.
I think you are exactly right about the PCM/main relay. It looks like it's not closing so nothing is getting powered up.
The first thing to do is get that check engine light working & that should fix this.
I think you are exactly right about the PCM/main relay. It looks like it's not closing so nothing is getting powered up.
The first thing to do is get that check engine light working & that should fix this.