C4 Fuel problem
Thread Starter
3rd Gear
Joined: Jun 2015
Posts: 3
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C4 Fuel problem
My 1984 C4 wont run. If I pour fuel down the carbs it fires up. I couldn't hear the pump start up so, I took out the fuel pump and checked for voltage at the pump, and I have a constant 12 volts to me that means the pump is bad, but wanted a second opinion. Since I read that I should have voltage for 2 seconds, and not constant voltage.
Drifting
Joined: Sep 2014
Posts: 1,579
Likes: 59
From: Trieste Italy
My 1984 C4 wont run. If I pour fuel down the carbs it fires up. I couldn't hear the pump start up so, I took out the fuel pump and checked for voltage at the pump, and I have a constant 12 volts to me that means the pump is bad, but wanted a second opinion. Since I read that I should have voltage for 2 seconds, and not constant voltage.
Thread Starter
3rd Gear
Joined: Jun 2015
Posts: 3
Likes: 0
Well I replaced the fuel pump, still wont run. I still have a constant 12 VDC at the pump, but no fuel to the carbs, and the pump still doesn't seem to be running even with the constant voltage at the pump, still runs if I put fuel straight into the carbs. anybody got any ideas before I take it to the shop.
Drifting
Joined: Sep 2014
Posts: 1,579
Likes: 59
From: Trieste Italy
If there is a constant 12 scab at pump fuse should be ok, have you check it anyway?
I don't know if exist or not but since that there is sca at pump but pump doesn't start would check for pump relay, surely it should be located after from where you measured dcv
I don't know if exist or not but since that there is sca at pump but pump doesn't start would check for pump relay, surely it should be located after from where you measured dcv
Last edited by Christi@n; Jun 30, 2015 at 11:06 AM.
Thread Starter
3rd Gear
Joined: Jun 2015
Posts: 3
Likes: 0
Thanks.
I've got a weird problem. I got it running, but I have that same 12 VDC even when the key is off. So the pump runs all the time now, so obviously I have a short I will need to hunt down. Thanks for the advice. Hope I can return the favor some time.
Tom
I've got a weird problem. I got it running, but I have that same 12 VDC even when the key is off. So the pump runs all the time now, so obviously I have a short I will need to hunt down. Thanks for the advice. Hope I can return the favor some time.
Tom
Safety Car
Joined: Sep 2004
Posts: 3,953
Likes: 550
From: Mission Viejo CA
That's interesting! From not running, to running all the time? Something strange here, or did you discover something you aren't telling us?
There are two current paths for operation of the fuel pump. Both feed power to the fuel pump fuse, located at the right end of the IP (instrument panel), bottom row, marked F.P. The fuel pump relay is located next to the windshield wiper motor. (Not the MAP sensor, which is above the brake booster.) The relay is actuated when you turn on the key, for about two seconds to pressurize the fuel system. If you don't start the engine, the fuel pump relay (and the pump) should turn off. If you do start the engine, the fuel pump relay is turned back on. The second current path is thru the Oil Pressure switch which actuates when the engine is running. Either of these can malfunction to keep your fuel pump running all the time. The Oil Pressure switch is located on the left (drivers) side of the engine, below the distributor.
Please don't call those Throttle Body Injectors "carbs". Big difference!
There are two current paths for operation of the fuel pump. Both feed power to the fuel pump fuse, located at the right end of the IP (instrument panel), bottom row, marked F.P. The fuel pump relay is located next to the windshield wiper motor. (Not the MAP sensor, which is above the brake booster.) The relay is actuated when you turn on the key, for about two seconds to pressurize the fuel system. If you don't start the engine, the fuel pump relay (and the pump) should turn off. If you do start the engine, the fuel pump relay is turned back on. The second current path is thru the Oil Pressure switch which actuates when the engine is running. Either of these can malfunction to keep your fuel pump running all the time. The Oil Pressure switch is located on the left (drivers) side of the engine, below the distributor.
Please don't call those Throttle Body Injectors "carbs". Big difference!
Last edited by Hot Rod Roy; Jun 30, 2015 at 04:59 PM.
Drifting
Joined: Sep 2014
Posts: 1,579
Likes: 59
From: Trieste Italy
Maybe that a stucked relay do not disconnect when key off
Basically relay is a switch turned on/off by another switch
I would to do this test
Locate f.p relay
Turn key on pump always runnin, then key off
Remove f.p relay and try to key on again, if pump no runs now there's a possibility that relay is culprit,
Christian
Last edited by Christi@n; Jun 30, 2015 at 06:05 PM.
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