Question about sensors
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Mountain Pass
Joined: Feb 2003
Posts: 136
Likes: 3
Question about sensors
I was talking to a guy who cant get his truck to start. Turns over but no power to fuel pump. Checked relays fuses inertia switch nothing. In my jeep 4.0 my cps went south and would let it start. But, i guess these engines dont have one.
Post Fiend
Joined: Nov 2002
Posts: 9,987
Likes: 7
From: Memphis, TN
Question about sensors
"Checked relays fuses inertia switch nothing."
Does that mean they didn't have power? When the key is turned on, the EEC (computer) relay comes on and the computer energizes the fuel pump relay for about 1 sec until the PIP (distributor pickup) indicates that the engine is turning, at which time the computer keeps the FP relay on. It sends power thru the inertia switch & the tank select switch to the pump.
Does that mean they didn't have power? When the key is turned on, the EEC (computer) relay comes on and the computer energizes the fuel pump relay for about 1 sec until the PIP (distributor pickup) indicates that the engine is turning, at which time the computer keeps the FP relay on. It sends power thru the inertia switch & the tank select switch to the pump.
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Mountain Pass
Joined: Feb 2003
Posts: 136
Likes: 3
Question about sensors
This distributor PIP...whats that all about. You said it indicated the engien is running? Would that be similer to the function of a CPS? BTW the fuel pump is getting no power. Said he checked the fuse...relay and the inirtia switch and all indicate are working ok. So, if this PIP, BTW what does that stand for and i assume it is in the distributor, is bad would it cause alot of bad ju jus including no power to fuel pump?
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Senior User
Joined: Jan 2002
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From: "tween the cotton and tob
Question about sensors
I believe the CPS only cuts out the spark. The fuel pump is controlled by the PCM as Steve said. The fuel injectors are power on with the key on one wire and grounded by the PCM to pulse. If you dont have that initial 1 to 2 sec cycle of the fuel pump when first turning on the key then check for voltages from the FP forward. A good schematic is invaluable. Am I on the right track here Steve?
Post Fiend
Joined: Nov 2002
Posts: 9,987
Likes: 7
From: Memphis, TN
Question about sensors
Yes, doc, but the PIP is almost the same as the CPS. The CPS is more accurate because it has more teeth on its tone ring (behind the harmonic balancer), but both just send a pulse for use in calculating ignition & fuel management. The PIP (Profile Ignition Pickup) only has as many teeth as the engine has cylinders and is connected to the ignition module which relays the signal to the EEC. If the PIP is pulsing, the EEC knows the engine is turning AND how fast. You can see it by removing the cap & rotor - it's the only other thing inside an EFI distributor.
tim
If the fuse, the relay, & the inertia switch are all good, then the only way the FP wouldn't "get power" is if the battery or fusible links are bad or if the EEC PWR relay isn't turning on. If the pump is getting power but "not working", then the FP is bad.
The Haynes manual covers all this in detail with pics, so get one & read all about it.
tim
If the fuse, the relay, & the inertia switch are all good, then the only way the FP wouldn't "get power" is if the battery or fusible links are bad or if the EEC PWR relay isn't turning on. If the pump is getting power but "not working", then the FP is bad.
The Haynes manual covers all this in detail with pics, so get one & read all about it.
New User
Joined: Feb 2003
Posts: 10
Likes: 0
From: Topsfield, Maine
Question about sensors
Hey,
I've got an 88 f-150 with a 300-6 that i've had the same problem with. I found 2 things- 1st the connections on the FP coroded, 2nd the ECM is grounded directly to the battery by 2 smaller wires that connect to the negative terminal at the battery. those lines coroded right there so that the computer lost its ground and didn't turn on the FP relay... that took me 2 days to find...the wire didn't break off of the terminal it was just hanging by the plastic casing.... the truck would run from time to time as long as you didn't move it... it was running and I got P.O.ed and slamed the hood... when I did the motor hitched... I knew then that it had to be wiring.... from there I just started shaking wires till I finally found it....don't know if this is any help or not but thought I'd throw it in
Good luck
Rhoadesy
I've got an 88 f-150 with a 300-6 that i've had the same problem with. I found 2 things- 1st the connections on the FP coroded, 2nd the ECM is grounded directly to the battery by 2 smaller wires that connect to the negative terminal at the battery. those lines coroded right there so that the computer lost its ground and didn't turn on the FP relay... that took me 2 days to find...the wire didn't break off of the terminal it was just hanging by the plastic casing.... the truck would run from time to time as long as you didn't move it... it was running and I got P.O.ed and slamed the hood... when I did the motor hitched... I knew then that it had to be wiring.... from there I just started shaking wires till I finally found it....don't know if this is any help or not but thought I'd throw it in
Good luck
Rhoadesy