Aftermarket fuel pump wiring question..

Signal 73

Signal 73

#2 is #1
Joined
Jul 30, 2006
Messages
1,124
when using the factory lift pump wire to trigger the relay for my aeromotive setup when the engine is running the lift pump wire does not send a steady 12 volts, it flucuates on off on off making the pump do the same.
Any ideas? this is on a 01 12 valve
Thanks!
 
Do you use the ECM for the 24V still? If so, could there be a fuel pressure sensor that is sensing 'adequate' pressure and telling the pump to cycle off?
 
PRattenbury said:
Do you use the ECM for the 24V still? If so, could there be a fuel pressure sensor that is sensing 'adequate' pressure and telling the pump to cycle off?
Click to expand...
Yes ECM is bolted up to the block. As far as I know there is no FP sensor.

When I turn it to the on position it will prime the pump for a 1/2 sec. or so which is normal. when I shut it off the pump runs for about 5 seconds. when its running the wire pulses on and off. Weird would like to figure this one out...:doh:
 
I'm not sure which sensor it would be, but when you first turn the key on, the fuel pump cycles on/off. After the engine starts, the pump recognizes the engine is running & then holds 12v constant to the fuel pump wire. You aren't getting that signal which keeps the pump running, could be the cam sensor or the crank sensor, not sure which one sends this signal.
 
it does the quick burst thing then once you start it and its running it send the pulsating signal. its an 01 so its got the cam sensor, which is working cause the tach and charging sys works.:confused:
 
Where did you test the wire at with your meter? At the relay? Possibly a bad connection where you hooked to the wire?
 
I checked the wire unplugged with my test light (with the relay wired hot off the battery) and at the relay with the wire plugged in. same results...keep the ideas coming.
 
I would try to find out what signal tells the ecm to turn the pump on & go from there. Possibly the crank sensor, but not sure. I do know that when I change my fuel filter, I bump the starter & the pump keeps running for 30 seconds till it builds pressure & shuts off. I then bump it again & it will run the pump another 30 seconds until pressure is built & shuts off. I repeat this sequence 3-4 times then it fires right up, no bleeding required. The pump doesn't continue to run until the truck is actually running. This tells me that it gets a signal from one of these 2 sensors showing the ecm that fuel is needed at a steady rate. Have you checked for codes?
 
Shoulda used a harness from a late 98 12 valve. We wouldn't be discussing this. Damn overvalved computer-controlled (%&$((%$. :bang
 
well if you us a rely set up to power the pump you can use a ground trigger or a positive trgger from the key
 
PRattenbury said:
Shoulda used a harness from a late 98 12 valve. We wouldn't be discussing this. Damn overvalved computer-controlled (%&$((%$. :bang
Click to expand...
:badidea: not ideal on the 01's there Paul. maybe on the 98.5-00 I think we discussed this already*bdh*
Was reading the latest TDR mag while on the can a few min ago and looks like fuel pump relay may be the culprit. a guy wrote in with similar concerns, we shall see!
 
what if the ecm senses the voltage load and turns off the pump ? and when the load is less i comes on ,,, if thats the case there nothing can be done but maybe put a one way diode in it ?????
 
That is something I will play around with today also thanks for the idea.
one thing with that though is all the guys I know running the fass dont have this issue..:pop:
 
You could use a one way diode. I would just find a ignition feed wire from inside of the cab to trigger the relay or just figure out what signal wire from the vp could cause the problem & run a 12v jumper wire across.
 
well I found a ground wire coming off the harness I never hooked up. all seems welll now, just like factory (but better!:evil )
 
You must log in or register to reply here.
Back
Top