C4 Fuel Pump will not start
Thread Starter
Instructor
Joined: Dec 2005
Posts: 108
Likes: 0
From: Gainesville Florida
C4 Fuel Pump will not start
I have an intermittent starting problem with my C4. The car would crank but not start. The spark was fine, but I discovered that the fuel pump was delivering 0 PSI when I would crank the car.
I replaced both the fuel pump relay and the fuel pump. The car ran fine for one day. The next morning I was back to the same problem -- the car will crank but no start. This problem only seems to happen when the car is cold.
I replaced both the fuel pump relay and the fuel pump. The car ran fine for one day. The next morning I was back to the same problem -- the car will crank but no start. This problem only seems to happen when the car is cold.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
Good Luck!
Melting Slicks
Joined: Feb 2008
Posts: 3,286
Likes: 6
From: Palm Beach
The oil pressure switch provides a backup source of power to the pump. It only functions when you have oil pressure. If the pump does not run when your turn the key, your problem is elsewhere.
Shouldn't take long to troubleshoot if you can read a schematic. It's a fairly simple system.
The FSM has a good troubleshooting chart.
Last edited by MK 82; Sep 1, 2008 at 12:17 PM.
Instructor
Joined: Apr 2005
Posts: 118
Likes: 0
From: Pensacola Florida
I have the same problem I'm trying to figure out in the general forum. Replaced the pump, relay, ignition module, coil, cap and rotor and still no fuel to the rail. Some how no power is getting to the pump when the engine is cranked. It rotates but will not start. If you get and answer I'm in the general forum. It will help and I will do the same. Thanks in advance.
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Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
You should run a wire from the positive terminal of the battery to pin G on the ALDL, that's the pin on the lower left side of the ALDL, that will bypass the fuel pump circuit and provide 12 volts to the fuel pump, if it runs you know you have a problem in the circuit. I once had a similar problem, had replaced the fp relay and it failed again. Upon examination I found the wires going into the relay base (and you have to pull it from the firewall to see it) the insulation had shrunk back an inch or so and wires were coming into contact with one another...easy fix. I posted it and found out alot of guys have found this to be a problem with our earlier C4s.
Thread Starter
Instructor
Joined: Dec 2005
Posts: 108
Likes: 0
From: Gainesville Florida
Thanks!
Just to confirm we are on the same page regarding the ALDL pin, in my manual it says PIN G is for CCM diagnostics. Usually, I ground pin G to pin A to get diagnostics to display on the dash. It seems strange that it will turn on the pump? Do I have the correct pin G?
Just to confirm we are on the same page regarding the ALDL pin, in my manual it says PIN G is for CCM diagnostics. Usually, I ground pin G to pin A to get diagnostics to display on the dash. It seems strange that it will turn on the pump? Do I have the correct pin G?
Last edited by ceberus; Sep 1, 2008 at 05:54 PM.
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
Sorry dude, I looked at your profile, I see yours is a 1992 (always best to post the year) so it might be different, I think 84-91 was OBD1 and the ALDL only has one pin on the lower row...left hand side, running 12 volts to that activates the fuel pump...but, like I said 92 maybe different.
Instructor
Joined: Apr 2005
Posts: 118
Likes: 0
From: Pensacola Florida
Sorry dude, I looked at your profile, I see yours is a 1992 (always best to post the year) so it might be different, I think 84-91 was OBD1 and the ALDL only has one pin on the lower row...left hand side, running 12 volts to that activates the fuel pump...but, like I said 92 maybe different.
lambert my car is and 87.
Instructor
Joined: Apr 2005
Posts: 118
Likes: 0
From: Pensacola Florida
You should run a wire from the positive terminal of the battery to pin G on the ALDL, that's the pin on the lower left side of the ALDL, that will bypass the fuel pump circuit and provide 12 volts to the fuel pump, if it runs you know you have a problem in the circuit. I once had a similar problem, had replaced the fp relay and it failed again. Upon examination I found the wires going into the relay base (and you have to pull it from the firewall to see it) the insulation had shrunk back an inch or so and wires were coming into contact with one another...easy fix. I posted it and found out alot of guys have found this to be a problem with our earlier C4s.
How far back did you have to chase the wire from the relay?
Thread Starter
Instructor
Joined: Dec 2005
Posts: 108
Likes: 0
From: Gainesville Florida
Hi Mike,
I have the FSM. Since the fuel pump will not even prime, I am assuming the problem is in the relay circuit. I am using schematics from Chart A-5 to troubleshoot the FP relay circuit.
The issue I am having at this time is that I am not smart enough in circuits to to correlate the five prongs on the relay to what is described in the diagram.
I have the FSM. Since the fuel pump will not even prime, I am assuming the problem is in the relay circuit. I am using schematics from Chart A-5 to troubleshoot the FP relay circuit.
The issue I am having at this time is that I am not smart enough in circuits to to correlate the five prongs on the relay to what is described in the diagram.
Burning Brakes
Joined: Apr 2004
Posts: 762
Likes: 2
From: Huntington ma
Jumper the pump (power "hot" lead and the lead out to the Pump itself) at the fuel pump relay - that Should have the pump running constantly, as long as you leave the jumper connected.
Normally the pump will run (the relay will be "on") for 2-3 seconds after the ignition key is turned to run. That's all - 2-3 seconds. This process is controlled by the ECM. The relay is NOT on during cranking so the fuel pump does NOT run during cranking.
Only if you crank it long enough for Oil pressure to come up does the oil pressure Switch then cause the fuel pump relay to come on and run the pump. As long as there is oil pressure the relay will be held On by that switch.
Simple enough...
Normally the pump will run (the relay will be "on") for 2-3 seconds after the ignition key is turned to run. That's all - 2-3 seconds. This process is controlled by the ECM. The relay is NOT on during cranking so the fuel pump does NOT run during cranking.
Only if you crank it long enough for Oil pressure to come up does the oil pressure Switch then cause the fuel pump relay to come on and run the pump. As long as there is oil pressure the relay will be held On by that switch.
Simple enough...
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
OnlyA1, what I said about jumping terminal G will/does work for an 87 (mines an 87). As far as the wires going into the FP relay...just pull it off the firewall and look at the wires going in...my bet is you'll see what I was referring to.
Melting Slicks
Joined: Feb 2008
Posts: 3,286
Likes: 6
From: Palm Beach
Unplug the connector. Take a fused lead and attach one end to the batt pos.
touch the other end to terminal E on the connector.
Does the pump run?
Last edited by MK 82; Sep 2, 2008 at 04:28 PM.