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Ecu and Fuel Pump


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8 replies to this topic

#1 A_DuB

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Posted 12 January 2005 - 05:26 PM

I'm still relatively new to USMB but have posted before. My previous post was concerning the same general problem but it never seemed to attract to many responses. I was never able to resolve this issue and therefore my car has just been sitting in the garage for the past two months. I can't take the car to a real mechanic because it wont start, don't want to have it towed because of too much snow and fears of having it get messed up in the process.

Which brings me here with my question. Does the ECM have anything to do with controlling the electricity to the fuel pump?

The reason I ask is that, is if any one remembers back about a month and a half ago I had a post asking about a fuel pump fuse. To make a reallllllllllly long story short, there is no fuel pump fuse just a relay, turns out it's working fine clicking like a mofo, so we turn to the fuel pump. Pulled it out and went and got a brand new one. Put it in and car still didn't run. So that's where I'm at now and have been at for the past month or so.

I've been able to talk to a few people about my problems with my car and one of the suggested that the car may have a "rollover sensor" witch may be stopping the fuel pump form working. This makes sense to me because before the car was fine and it had just suddenly stop working after doing routine maintenance in which the car partially fell of one of the ramps.

I have both Chilton's and Hayne's books neither of witch mention anything close to a rollover sensor and my best guess would be that the Ecu controls the fuel pump. I'm at a 100% loss at this point and have no other direction to turn and would be very grate full for any type of response at this point.

#2 Legacy777

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Posted 12 January 2005 - 08:40 PM

Yes, the ECU triggers the fuel pump relay to turn on.


The rollover valve is mechanical, and not electronic, so it's probably not that. Have you put a tester on the fuel line to see if there is any pressure at any time?

#3 SevenSisters

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Posted 12 January 2005 - 08:44 PM

My '91 AWD has a roll-over valve that only appears to be part of the evaporative system and not the fuel delivery system. Never have had to trouble shoot a problem but here's how i'd start:

Does the fuel pump run? Can you hear it when the ignition is switched to the ON, but not crank position?
IF yes, check the fuel filter and pressure regulator.
See if the injectors are getting gas. Be careful.
IF no, is there juice to the pump connector at the pump.
IF yes, check for continuity of the motor. Then take it out and hook it up to 12 Volts and see if it runs for a second.
If no, start checking continuity back to the relay.
I don't see how the ECU would stop power to the pump but it probably is tied to the canister purge valve and pressure regulator.
The fuel system appears to be relatively simple. Are you getting any codes?

#4 SevenSisters

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Posted 12 January 2005 - 08:50 PM

I was typing while Josh replied. Have to go with him on the ECU and relay relationship.

#5 sea#3

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Posted 12 January 2005 - 09:06 PM

Like SevenSisters and Legacy 777 have pointed out checking for power at the pump would be a good start and work your way back to the relay ,then check for the signal from the ECM
You may want to check the connector for the fuel pump which is under the rear seat lower cushion (on the passenger side ) there is a connector there (that for some reason on turbo's) tend to burn and cause an open circuit

Hope this helps
SEA#3

#6 Cougar

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Posted 12 January 2005 - 10:55 PM

I owned an '88 GL-10 that had a fuel pump problem. The ECU controlled the ground lead connection to the pump. I found the problem in the ECU and replaced the bad transistor. I suspect that the pump on your vehicle may be controlled the same way. Hard to say the ECU may be bad though, it would be one of my last guesses really. I would suspect the lack of a signal from one of the engine sensors may be causing this. You may find a clue to this problem by checking the ECU codes. Check all the fuses also.

#7 Legacy777

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Posted 13 January 2005 - 09:11 AM

I was looking through some diagrams last night, and both pins of the fuel pump relay are actually tied to the ecu

http://www.surrealmi...electrical1.jpg

#8 A_DuB

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Posted 13 January 2005 - 03:16 PM

No i have no fuel pressuer tester, but the injectors aren't getting any gas what so ever. There are 12v at the connecter of the fuel pump, and the old fuel pump that I replaced for $130 still works when i hook it up directly to the battery.

#9 Cougar

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Posted 13 January 2005 - 03:24 PM

Can you hear the pump run for a couple seconds when you turn the key to the run position? You may have to crank it first then try again.

When you measured the voltage to the pump did you measure across the wires to the pump only and not to ground? If you didn't, then you need to do it that way.




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