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David_DuBois
Jedi Warrior
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Kerosene is a good working fluid for testing the fuel pumps, except that it has a pretty strong odor. I switched over to mineral spirits and like it much better.
Cheers,
Cheers,
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SU Fuel Pump ReBuild
- Thread starter DenverMGB
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OP
DenverMGB
Freshman Member
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Progress Report....
I bought some mineral spirits and an extra length of fuel hose. I ran the pump from the cigar lighter on my Trailblazer in/out of about a pint of liquid for 2 1/2 hours without any problems at all. I got good flow and the pump stopped when I closed the outlet off. So far, so good.
Next, I mounted the pump back under the car, connected up the new fuel hoses, a new vent hose, the ground and live wires. I reconnected the battery and turned the ignition on and .... nothing ....
I pulled the live connector off the pump, tapped the spade and got a spark and a very quiet clunk from the pump. Like the coil was trying to pull the diaphragm but didn't have enough power. A voltmeter (digital) from the spade to ground showed 8.6 V; without the pump in the circuit I got 11.5 V.
From before all this started, I know the battery is strong enough to turn the starter and my neighbour's tester showed 300A and 11.5 V under load but it was completely flat when I came to bring the car back to life after its very long winter lay-up - 9 months! My neigbour kindly let me his charger and we left it trickle-charging for 3 days. After which, as I said, it we strong enough to turn the engine over. I've left the battery disconnected whilst I worked on the pump so as not to drain it uneccesarily.
Where to go from here? I could try to run the mounted pump from the Trailblazer just to check it hasn't suffered some problem during the mounting (I didn't drop it!). Any ideas?
I bought some mineral spirits and an extra length of fuel hose. I ran the pump from the cigar lighter on my Trailblazer in/out of about a pint of liquid for 2 1/2 hours without any problems at all. I got good flow and the pump stopped when I closed the outlet off. So far, so good.
Next, I mounted the pump back under the car, connected up the new fuel hoses, a new vent hose, the ground and live wires. I reconnected the battery and turned the ignition on and .... nothing ....
I pulled the live connector off the pump, tapped the spade and got a spark and a very quiet clunk from the pump. Like the coil was trying to pull the diaphragm but didn't have enough power. A voltmeter (digital) from the spade to ground showed 8.6 V; without the pump in the circuit I got 11.5 V.
From before all this started, I know the battery is strong enough to turn the starter and my neighbour's tester showed 300A and 11.5 V under load but it was completely flat when I came to bring the car back to life after its very long winter lay-up - 9 months! My neigbour kindly let me his charger and we left it trickle-charging for 3 days. After which, as I said, it we strong enough to turn the engine over. I've left the battery disconnected whilst I worked on the pump so as not to drain it uneccesarily.
Where to go from here? I could try to run the mounted pump from the Trailblazer just to check it hasn't suffered some problem during the mounting (I didn't drop it!). Any ideas?
David_DuBois
Jedi Warrior
Offline
DrEntropy said:
Or the line supplying power to the pump - very possibly in the bullet connector in the engine compartment. See the article, Electrical Connection Preparation under the Other Tech Articles section of my Web site at: https://homepages.donobi.net/sufuelpumps/
Cheers,
OP
DenverMGB
Freshman Member
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Thanks for all your help. Here's an update...
Checked the grounding and tried an alternate ground point without sucess.
Looked around the engine compartment but couldn't find the right connector.
Whilst checking around I noticed that the voltage at the pump went up slightly if I disconnected the coil so got my friendly neighbour to re-check the battery. He found a dead cell so I took it back to Sears for a discount on a new one since it was still under their pro-rated warranty. They tested it and agreed with the diagnosis.
Fitted the new battery but dissapointment,,,no change. Still nothing from the pump but the starter motor kicks just fine. Still 8.6 V at the pump when connected, 11.8 V (up slightly) when disconnected. So I think I'm back to the supply line. I checked a wiring diagram from Advance AutoWire and the Haynes manual but they don't have enough detail for me to be able to identify the route the power to the pump takes.
Checked the grounding and tried an alternate ground point without sucess.
Looked around the engine compartment but couldn't find the right connector.
Whilst checking around I noticed that the voltage at the pump went up slightly if I disconnected the coil so got my friendly neighbour to re-check the battery. He found a dead cell so I took it back to Sears for a discount on a new one since it was still under their pro-rated warranty. They tested it and agreed with the diagnosis.
Fitted the new battery but dissapointment,,,no change. Still nothing from the pump but the starter motor kicks just fine. Still 8.6 V at the pump when connected, 11.8 V (up slightly) when disconnected. So I think I'm back to the supply line. I checked a wiring diagram from Advance AutoWire and the Haynes manual but they don't have enough detail for me to be able to identify the route the power to the pump takes.
OP
DenverMGB
Freshman Member
Offline
Close, good doctor, close. It was a twist-on connector, just below the inertia switch (which I fanally located just now) in the live feed to the fuel pump where someone had installed an inline fuseholder. I jiggled it a bit and wow - the pump sprang in to life.
I don't think a fuse is recommended to the fuel pump is it?
I don't think a fuse is recommended to the fuel pump is it?
David_DuBois
Jedi Warrior
Offline
DenverMGB said:
An in line fuse in the white wire going to the pump is a very good idea. A 10 amp fuse could save a wire harness from going up in smoke if that line becomes shorted. Get rid of the twist on connectors and use some of the Posi-lock connectors (available from NAPA).
Cheers,
