M
manic
Guest
The 10amp fp fuse is blowing. I am only able to drive a short distance before it blows. (2x now) what could be the cause? Do I need to replace the fuel pump?
boomdriver
Well-known member
Thats actually the fuel pump relay fuse, as the book decribes it, so I'd look at the $10 relay first, and its sister circuits in the oil pressure switch.
If that does not fix it, look for a short between the relay and the tank. I doubt that its the pump....for the pump to create enough resistance to blow the fuse??? it would have to lock up and even then, I don;t think that would do it.
This is more of a short in wire or the relay is fried.
- Thread starter
- #3
M
manic
Guest
Thanks for the quick reply. Where would I find the relay and the oil pressure switch? If it makes a difference my corvette is a 1986.
boomdriver
Well-known member
well....the relay should be between the brake booster and the engine cyl head...mounted on the firewall or the booster. It has 5 wires, 1 heavy gauge wire at each end of the plug. Those would be the power wires, in/out.
The oil press switch is on the backside of the left cyl head. there are 2 switches there on a single hollow T bolt....one is oil pressure and the one you care about isw the 2 wire pressure switch. Thats designed to give your power an alternate route to supply the fuel pump IF the pump relay ever/does fail......so when the relay fails the oil switch sends power as long as there is oil pressure.
If you DO pull the pump assy out, test it with a 12V source to confirm it runs before installing and bolting ALL those bolts in...remember, pump should run 2 seconds with key ON and then no more until the engine fires and runs.
Good Luck !
- Thread starter
- #5
M
manic
Guest
I will look at testing the relay tomorrow and let you know what I find. Even though you gave a good description of where I should find it I am not confident that I will be able to locate it. The brake booster would be near the Master Cylinder I'm guessing. I will look around there.
vetteoz
Well-known member
Fuse is after relay and OP switch so if fuse is blowing there is a overload or short to ground between fuse and pump
gmjunkie
Well-known member
My guess is the fuel pump is the culprit,I've had them act Exactly this way several times!~!!
boomdriver
Well-known member
Fuse is after relay and OP switch so if fuse is blowing there is a overload or short to ground between fuse and pump
Interesting...
I did not look at the drawing, but went by the label or ID in the book and on the fuse panel...FPR Fuel Pump Relay.
By that I assumed that it was fused to break power to the relay.
- Thread starter
- #9
M
manic
Guest
Dang it. I liked the first answer better. It seemed easier and cheaper. 
I have a full tank, I suppose I have to drain it somehow before I can get to the fuel pump. Is there a way for me to test it? It seems to be ok under idle. Could it be the sending unit?
I have a full tank, I suppose I have to drain it somehow before I can get to the fuel pump. Is there a way for me to test it? It seems to be ok under idle. Could it be the sending unit?- Moderator
- #10
vetteboy86
Well-known member
The fuel pump is extracted through the top of the top of the tank. You will need to remove the fuel filler door, and the rubber boot that is beneath. This may be brittle so take car as not to rip it. Once that is removed, you should see everything you need to pull the pump.
Schrade
Well-known member
The fuse blows because too much power is going through it.
Think of it as water flow.
The spigot is the battery. Turn it on, you get flow. Put on a hose, water flows through it. Put a sprayer on the hose, and none flows, unless you squeeze the trigger (potentiometer).
The fuse is a small spot in the hose, like the hourglass constriction, sort of. With the sprayer off, no flow, the constriction is fine. Squeeze the sprayer, it flows. Max the sprayer, and the constriction is gonna' get stressed, til it blows.
A cut in the hose (short to ground), AFTER the constriction, will max flow, til it blows the fuse. A cut BEFORE the fuse WON'T make it blow, but will make the sprayer dribble.
Your multimeter helps you 'see' the flow. The water won't go anywhere, unless it can hit the 'ground'.
Think of it as water flow.
The spigot is the battery. Turn it on, you get flow. Put on a hose, water flows through it. Put a sprayer on the hose, and none flows, unless you squeeze the trigger (potentiometer).
The fuse is a small spot in the hose, like the hourglass constriction, sort of. With the sprayer off, no flow, the constriction is fine. Squeeze the sprayer, it flows. Max the sprayer, and the constriction is gonna' get stressed, til it blows.
A cut in the hose (short to ground), AFTER the constriction, will max flow, til it blows the fuse. A cut BEFORE the fuse WON'T make it blow, but will make the sprayer dribble.
Your multimeter helps you 'see' the flow. The water won't go anywhere, unless it can hit the 'ground'.
boomdriver
Well-known member
Dang it. I liked the first answer better. It seemed easier and cheaper.
Pulling the pump is not that difficult...
with tools it can be done in 20 minutes.
Warning: the boot thats around the filler neck will most likely tear. They get brittle.
Advice:
have some proper size Fuel Injection Hose there,. to mend any lines that tear or have to be cut off. Have a few worm gear clamps as well.
You do NOT have to drain the tank. Being full just makes it easier to splash fuel going in/out. Use good judgement and caution. An open tank with a few gallons has lots of vapors... Make some kind of cover (cardboard in a plastic bag) to lay over the hole in the tank while you replace the pump on the bench.Not a rag that can act like a wic.
Do all this with open air circulating and no chance of sparks. Fuel vapors tend to collect low and build up.
- Thread starter
- #13
M
manic
Guest
I appreciate all the assistance. I found a diagnostic chart on autozone's website. It says to probe the ALCL connector terminal "G" (after disconnecting the fuel pump at the rear body connector and ignition off). If the light is on then there is a short in ckt 120. If the light is off then it is either ckt 120, fuel pump or pump harness. Were is the ALCL connector. What does it look like? How do I test it?
I hope links are allowed. I searched the FAQ and didn't see anything aginst it. | Repair Guides | Cross-fire Injection System | Fuel Pump | AutoZone.com
I hope links are allowed. I searched the FAQ and didn't see anything aginst it. | Repair Guides | Cross-fire Injection System | Fuel Pump | AutoZone.com
Schrade
Well-known member
The ALDL connector is underneath the dash, just above where your knees would be:
The generic link is an ok start, but you'll need the year-specific info for PROPER diagnostic tests.
The generic link is an ok start, but you'll need the year-specific info for PROPER diagnostic tests.
vetteoz
Well-known member
With your DVM set on Ohm's , a fresh fuse in and the wiring at pump disconnected
you put one lead on Terminal G and the other to a good ground point.
You should get no reading , if you do there is a connection to ground before pump
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- #16
M
manic
Guest
The diagnostics actually says to do a light test. I tried using the A terminal for ground and got no reading. I got nothing whether the fuel pump was connected or not. It was suggesting if the light comes on then it means there is a short in the circuit. If there is no light then it could be an intermittant short in the circuit or a bad fp. I tried your 'ohm' test and did get a reading with the fp disconnected.
I got the fuel pump out. I am going to go ahead and replace it. Any opinions on the Airtex Master Fuel Pump?
I got the fuel pump out. I am going to go ahead and replace it. Any opinions on the Airtex Master Fuel Pump?
gmjunkie
Well-known member
It'l work just fine!
vetteoz
Well-known member
Test light should have lit up when Terminal A probed ( light direct to ground ); does test light work correctly?
( you didn't have test light between G and A did you ? )
That would indicate to me you have a short in the wiring before the tank connector
Putting meter leads between terminal G and a ground should show no connection to ground with tank plug disconnected
Schrade
Well-known member
This is why GMJunkie suggests cleaning ground contacts. Oxidation buildup increases resistance, and you lose the connection.
Judging by what you say, the ground is faulty - NOT connected to the frame anywhere. If you're sure you had power coming INTO the test light, and you then probed the 'A' socket, and the light didn't light, then either the test light is toast, or the ground connection isn't connected.
Try probing directly to ground with the light and see if it comes on. Post back on it.
- Thread starter
- #20
M
manic
Guest
I was using terminal A as the ground, with the positive on G. Using the probe that way I had resistance but no voltage.
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