Need Help with Fuel Pump Problem
Thread Starter
Melting Slicks
Joined: Mar 2008
Posts: 2,141
Likes: 76
From: Santa Maria, CA
Need Help with Fuel Pump Problem
A couple days a go I took my 85 for a spirited drive over a windy mountain road. On the back side of the hill the engine quit without warning. When I tried to restart it I realized the fuel pump was not running. I assumed a bad pump and had the car towed home. After I got it home I tried to start it again. Still no pump. I ordered a new pump. Today I thought I would try it again and to my surprise the pump ran and the engine started.
What else should I be looking at? Pump relay? Ignition module? I'm stumped.
What else should I be looking at? Pump relay? Ignition module? I'm stumped.
Thread Starter
Melting Slicks
Joined: Mar 2008
Posts: 2,141
Likes: 76
From: Santa Maria, CA
Thanks Tim. I hate these intermittent problems.
The pump is a Walbro with less than 5000 miles on it. From what I've heard, pumps don't fail intermittently.
I wondered about the relay. But I thought that once there's oil pressure the oil pressure switch completes the circuit for pump power. I have a new relay so there's no harm in replacing it.
So I'm thinking maybe an ignition problem. If the ECM doesn't get a reference signal it shuts off the fuel. Either the ignition module or the coil could be a problem. But again the intermittent nature has me wondering. I remember seeing a service bulletin that the coils were subject to heat problems.
Otherwise the car is running great. I got the new transmission in. I am now feeling the power of the 396 and it feels good.
The pump is a Walbro with less than 5000 miles on it. From what I've heard, pumps don't fail intermittently.
I wondered about the relay. But I thought that once there's oil pressure the oil pressure switch completes the circuit for pump power. I have a new relay so there's no harm in replacing it.
So I'm thinking maybe an ignition problem. If the ECM doesn't get a reference signal it shuts off the fuel. Either the ignition module or the coil could be a problem. But again the intermittent nature has me wondering. I remember seeing a service bulletin that the coils were subject to heat problems.
Otherwise the car is running great. I got the new transmission in. I am now feeling the power of the 396 and it feels good.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
OP switch ( if working ) supplies power direct to the pump bypassing the relay
To the injectors
Pump should still run from the OP switch once oil pressure is above 4 psi
3rd Gear
Joined: Oct 2012
Posts: 3
Likes: 0
From: Massachusetts
No power to ignition
Was running before I checked injectors with test light, then at the last injector during start the check engine light came on. Then tried starting car again and nothing happened no lights no nothing. No blown fuses
Le Mans Master
Joined: Mar 2002
Posts: 5,889
Likes: 2
From: Castro Valley Calif.
St. Jude Donor '03 thru '26
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When you pull the tank/sender/pump assy up and out of the tank, look closely at the small electrical plug on the UNDERSIDE of the sender plate assy...that is a very fragile little 3 pin plug that is held by just a C-clip and it gets loose and breaks contact. Ground or power..doesn't matter, the pump stops. You can slap the back of the car and it might start running again.
I had a problem just like what you describe...car would die at a stop lite or running 45 mph down the road like the key was turned off. After MUCH searching and 1 tow...I pulled the plate off to access the pump and the plug in fell off the connector!
The hard part was that there was always power to the plug outside the tank so I assumed that the pump was at fault. I even installed an old pump and the same stuff happened.. If I had not seen that elec plug-in fall off I'd have never known.
I had a problem just like what you describe...car would die at a stop lite or running 45 mph down the road like the key was turned off. After MUCH searching and 1 tow...I pulled the plate off to access the pump and the plug in fell off the connector!
The hard part was that there was always power to the plug outside the tank so I assumed that the pump was at fault. I even installed an old pump and the same stuff happened.. If I had not seen that elec plug-in fall off I'd have never known.
Thread Starter
Melting Slicks
Joined: Mar 2008
Posts: 2,141
Likes: 76
From: Santa Maria, CA
When you pull the tank/sender/pump assy up and out of the tank, look closely at the small electrical plug on the UNDERSIDE of the sender plate assy...that is a very fragile little 3 pin plug that is held by just a C-clip and it gets loose and breaks contact. Ground or power..doesn't matter, the pump stops. You can slap the back of the car and it might start running again.
I had a problem just like what you describe...car would die at a stop lite or running 45 mph down the road like the key was turned off. After MUCH searching and 1 tow...I pulled the plate off to access the pump and the plug in fell off the connector!
The hard part was that there was always power to the plug outside the tank so I assumed that the pump was at fault. I even installed an old pump and the same stuff happened.. If I had not seen that elec plug-in fall off I'd have never known.
I had a problem just like what you describe...car would die at a stop lite or running 45 mph down the road like the key was turned off. After MUCH searching and 1 tow...I pulled the plate off to access the pump and the plug in fell off the connector!
The hard part was that there was always power to the plug outside the tank so I assumed that the pump was at fault. I even installed an old pump and the same stuff happened.. If I had not seen that elec plug-in fall off I'd have never known.