Fuel pump blues.. halppppp!!!
Thread Starter
Burning Brakes
Joined: Nov 2008
Posts: 1,159
Likes: 31
From: Orange Park Florida
Fuel pump blues.. halppppp!!!
Hey there Gents, advice appreciated.. I just finished replacing the cracked console base on my 1987 C4. Afterwards, I l started car and it ran about 8 minutes then sounded like it ran out of fuel. I put around 7 gallons in it and went to restart it. It did not restart so i checked the fuel rail and no fuel was there.I also noticed the fuel pump was not running for 15 to 20 seconds when the key is first turned on.
I checked the voltage at the fuel pump connector and it was 11 volts. but keep in mind my fluke meter was last calibrated 10 or more years ago. I suspect it could be fuel pump relay since the fuel pump was recently changed by me and worked fine. I am thinking the relay sends a neutral to the pump when it closes.. like the cooling fans do.. does anyone have a idea that i can try.. thanks, gary
I checked the voltage at the fuel pump connector and it was 11 volts. but keep in mind my fluke meter was last calibrated 10 or more years ago. I suspect it could be fuel pump relay since the fuel pump was recently changed by me and worked fine. I am thinking the relay sends a neutral to the pump when it closes.. like the cooling fans do.. does anyone have a idea that i can try.. thanks, gary
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
Relay sends battery voltage to the pump.
Relay should only send Bat volts to the pump for ~2 seconds after key on, AND any time there is a reference pulse from the distributor (either cranking or running).
Also, once your engine builds ~4 PSI oil pressure, there is an oil pressure switch that should close, and send a parallel, Bat volts to the pump, so the car will run (with extended crank time at start up) even if the relay fails.
You shouldn't have seen 11v at the pump, unless it was during cranking or right after a key-on.
Relay should only send Bat volts to the pump for ~2 seconds after key on, AND any time there is a reference pulse from the distributor (either cranking or running).
Also, once your engine builds ~4 PSI oil pressure, there is an oil pressure switch that should close, and send a parallel, Bat volts to the pump, so the car will run (with extended crank time at start up) even if the relay fails.
You shouldn't have seen 11v at the pump, unless it was during cranking or right after a key-on.
Thread Starter
Burning Brakes
Joined: Nov 2008
Posts: 1,159
Likes: 31
From: Orange Park Florida
Thanks
Thanks, I will go recheck at the line side of the connector with the key on. the battery had gone bad (shorted cell while i was working on console change out. I put a brand new 635 amp die hard gold battery in it yesterday.. so it does have a good battery now.. i will check the connector volts now.
Relay sends battery voltage to the pump.
Relay should only send Bat volts to the pump for ~2 seconds after key on, AND any time there is a reference pulse from the distributor (either cranking or running).
Also, once your engine builds ~4 PSI oil pressure, there is an oil pressure switch that should close, and send a parallel, Bat volts to the pump, so the car will run (with extended crank time at start up) even if the relay fails.
You shouldn't have seen 11v at the pump, unless it was during cranking or right after a key-on.
Relay should only send Bat volts to the pump for ~2 seconds after key on, AND any time there is a reference pulse from the distributor (either cranking or running).
Also, once your engine builds ~4 PSI oil pressure, there is an oil pressure switch that should close, and send a parallel, Bat volts to the pump, so the car will run (with extended crank time at start up) even if the relay fails.
You shouldn't have seen 11v at the pump, unless it was during cranking or right after a key-on.
Burning Brakes
Joined: Jun 2005
Posts: 1,191
Likes: 15
From: Wallingford Vermont
Don't quote me on this: but it was my understanding that all Fluke digital multimeters are self calibrating. Hold the leads together and turn the unit on to Ohm scale - presto calibrated.
Instructor
Joined: Nov 2011
Posts: 147
Likes: 0
From: Florida
I would put a pressure gauge in place where you can see it. Hood closed take it for a ride.
Then turn key see if you get pressure. If not turn key off wait 20 seconds and turn key see if you get pressure. If not pressure wait a little longer say 30 seconds. After a few tries at that you should have pressure.
If not try cranking it about 5 second blasts a few times till you see pressure.
If you do not get pressure then you know something is up. I would run leads from connector at pump under the rubber at the filler so I could be in the car manipulate the key and see the fuel pressure gauge and see the VOM.
If you have no pressure but the VOM shows voltage each time it should KEY ON, CRANK, then it is inside the tank,
It could be the pump or it could be the assembly.
I had a NEW assembly and the connector on it was bad so I had 12 volts under the rubber mat but not twelve volts at the pump itself inside the tank.
Then turn key see if you get pressure. If not turn key off wait 20 seconds and turn key see if you get pressure. If not pressure wait a little longer say 30 seconds. After a few tries at that you should have pressure.
If not try cranking it about 5 second blasts a few times till you see pressure.
If you do not get pressure then you know something is up. I would run leads from connector at pump under the rubber at the filler so I could be in the car manipulate the key and see the fuel pressure gauge and see the VOM.
If you have no pressure but the VOM shows voltage each time it should KEY ON, CRANK, then it is inside the tank,
It could be the pump or it could be the assembly.
I had a NEW assembly and the connector on it was bad so I had 12 volts under the rubber mat but not twelve volts at the pump itself inside the tank.
Drifting
Joined: Jun 2013
Posts: 1,590
Likes: 60
From: ft myers FL/Munising MI
your fuel pump runs for 2 seconds after key on.....you should have pressure at the rail....if you have recently installed a new pump, you may have loose line into the pulsator....blows out when key on....you should be able to hear it for two secs....
I also believe providing 12 v to "e" on your aldl should start your pump....could be "g'...you'll have to check it out.....there are several threads regarding this....
I also believe providing 12 v to "e" on your aldl should start your pump....could be "g'...you'll have to check it out.....there are several threads regarding this....
Last edited by playsdixie; Dec 12, 2014 at 05:24 PM.
Racer
Joined: Oct 2012
Posts: 265
Likes: 5
From: Phoenix AZ
Before you go wracking your brains out, take the fuel pump out and make sure the connector is okay. I went through all the testing, swapping, metering, and replacing of the pump. Turned out the connector had disintegrated. How the car didn't catch fire I dont know.
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Thread Starter
Burning Brakes
Joined: Nov 2008
Posts: 1,159
Likes: 31
From: Orange Park Florida
arrgghhhh the saga continues..
Thanks for the help and the replys fellows, After tracing everything with the fsm electrical supplement.. I found all was in order. I then tested and replaced faulty 1 year old fuel pump. vette fired up and ran fine.. then started surgeing like a carbeurated car does when it is oscillating. It acts like it runs low on fuel then almost cuts off and the fuel pump catchs up. So it then idles up.. rpms increase and then roughly a minute later.. starves for fuel again.
It is strange because before this it ran steller.. all this from a dead battery. I did find the egr vale at the egr pipe had been disconnected.. I bought a new male oem connector and connected it.. i will unhook it today.
It is strange because before this it ran steller.. all this from a dead battery. I did find the egr vale at the egr pipe had been disconnected.. I bought a new male oem connector and connected it.. i will unhook it today.
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
Confirmed with a pressure gauge?
Thread Starter
Burning Brakes
Joined: Nov 2008
Posts: 1,159
Likes: 31
From: Orange Park Florida
Fixed it,,, hooray!!!
Thanks for your help guys... I found the problem.. it was my own lack of paying attention.. I had disconnected the vacuum line to the power brake booster. It is directly in the way of the battery disconnect switch. So I had to unhook it too put new battery in the car. I had installed a new conole base,console sides and cleaned the carpets when i was putting in my new pioneer amplifiers.. well the L98 is running pristine again now.. all is well, lesson learned... cars don't run well with a large vacuum line left unattached.. thanks again, Gggg
Racer
Joined: Oct 2012
Posts: 265
Likes: 5
From: Phoenix AZ
Thanks for your help guys... I found the problem.. it was my own lack of paying attention.. I had disconnected the vacuum line to the power brake booster. It is directly in the way of the battery disconnect switch. So I had to unhook it too put new battery in the car. I had installed a new conole base,console sides and cleaned the carpets when i was putting in my new pioneer amplifiers.. well the L98 is running pristine again now.. all is well, lesson learned... cars don't run well with a large vacuum line left unattached.. thanks again, Gggg