Checking fuel pump relay...
Thread Starter
TECH Apprentice
Joined: May 2006
Posts: 308
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From: Nebraska
Checking fuel pump relay... Guys,
After installing a walbro 255 pump twice and not having it work.....I used a 12-volt light test on the fuel pump relay (connected ground, stuck probe into PRIME fuel pump terminal in electrical center, turned ignition on) and the test light didn't light up ..... so I'm assuming the relay is bad. I'm replacing it tonight...but is there anything else I could be missing?...would disconnecting the cable from the negative battery terminal when dropping the tank (per Haynes instruction) prior to installing the pump have caused any electrical problems (shorts, surges,e tc...). I had no problem with the pump itself...the harness was straight forward, everything fit nicely. Any ideas?.....
Stroker2112
After installing a walbro 255 pump twice and not having it work.....I used a 12-volt light test on the fuel pump relay (connected ground, stuck probe into PRIME fuel pump terminal in electrical center, turned ignition on) and the test light didn't light up ..... so I'm assuming the relay is bad. I'm replacing it tonight...but is there anything else I could be missing?...would disconnecting the cable from the negative battery terminal when dropping the tank (per Haynes instruction) prior to installing the pump have caused any electrical problems (shorts, surges,e tc...). I had no problem with the pump itself...the harness was straight forward, everything fit nicely. Any ideas?.....
Stroker2112
Electrical troubleshooting advice to a Rush fan
Originally Posted by Stroker2112
Guys,
After installing a walbro 255 pump twice and not having it work.....I used a 12-volt light test on the fuel pump relay (connected ground, stuck probe into PRIME fuel pump terminal in electrical center, turned ignition on) and the test light didn't light up ..... so I'm assuming the relay is bad. I'm replacing it tonight...but is there anything else I could be missing?...would disconnecting the cable from the negative battery terminal when dropping the tank (per Haynes instruction) prior to installing the pump have caused any electrical problems (shorts, surges,e tc...). I had no problem with the pump itself...the harness was straight forward, everything fit nicely. Any ideas?.....
Stroker2112
After installing a walbro 255 pump twice and not having it work.....I used a 12-volt light test on the fuel pump relay (connected ground, stuck probe into PRIME fuel pump terminal in electrical center, turned ignition on) and the test light didn't light up ..... so I'm assuming the relay is bad. I'm replacing it tonight...but is there anything else I could be missing?...would disconnecting the cable from the negative battery terminal when dropping the tank (per Haynes instruction) prior to installing the pump have caused any electrical problems (shorts, surges,e tc...). I had no problem with the pump itself...the harness was straight forward, everything fit nicely. Any ideas?.....
Stroker2112
With respect to checking a relay, you should be able to switch the fuel pump relay with another standard 5 pin relay within the underhood electrical center and then check that device before you actually spend $$$ on another relay (which may or may not be the problem).
Pull one of your headlight relays and place your suspect fuel pump relay there; does the lamp work? If it does, your issue is not the relay. Check the fuel pump wires for shorts and opens if the relay is fine.
FYI,
MLE
Last edited by great421; Jan 2, 2007 at 12:42 PM. Reason: spelling
Neil!?!
Originally Posted by Stroker2112
Neil,
Excellent, thank you...
Geddy
Excellent, thank you...
Geddy
Don't you ever mention THAT name again; he can't drum nor can he write lyrics!
I'm the forgotten "Pete Best" of the Frozen North!
"Finding my way" now that was drumming perfection! YYZ - Boring!
(Seriously, it that a bit too obsure of a Rush rant or what...)
MIKE
(My little brother is Alex, my #1 son is Geddy, while #2 is Neil; I'm just a singer, which, by definition is NOT a musician!)
Thread Starter
TECH Apprentice
Joined: May 2006
Posts: 308
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From: Nebraska
Yes....Exit stage left, Subdivisions, and some of the other earlier stuff(2112)....all heavily influenced my early musical years (drumming). Still listen but don't play much anymore...would rather work/tune on the 408cid in my garage. Nonetheless, the relay is fine (thanks for the tip).....I think the fact that my tank is dropped w/ the electrical connectors disconnected is whats causing the test light not to light up. I'll put in a brand new fuel pump and if it still doesn't work....then I'll know its somewhere in the PCM/circuit between electrical center and tank.
Best Regards,
Bytor/Snowdog
Best Regards,
Bytor/Snowdog
The fuel pump relay cannot be swapped with a normal relay, the pins are of a different configuration. And the relay is bigger than normal as well.
To test the relay, simply apply voltage to the prime connector. As far as I remember from the wiring diagrams, the prime connector wire splices into the wire used by the pcm to turn the FP on or off. So applying 12v to the prime connector will do the same thing as the pcm turning the FP on or off.
If it makes the pump come on, you have a problem with the signal from the pcm and the relay is fine.
If it does not, then your problem is either the relay or the ground for the relays 'trigger' circuit.
Wait, this is all from experience with my LT1 car, the circuit on yours may(probably is slightly) be different. But I have the wiring diagram so I'll take a peek tonight and report back in the AM.
To test the relay, simply apply voltage to the prime connector. As far as I remember from the wiring diagrams, the prime connector wire splices into the wire used by the pcm to turn the FP on or off. So applying 12v to the prime connector will do the same thing as the pcm turning the FP on or off.
If it makes the pump come on, you have a problem with the signal from the pcm and the relay is fine.
If it does not, then your problem is either the relay or the ground for the relays 'trigger' circuit.
Wait, this is all from experience with my LT1 car, the circuit on yours may(probably is slightly) be different. But I have the wiring diagram so I'll take a peek tonight and report back in the AM.
Relays Different?
Originally Posted by Fire67
The fuel pump relay cannot be swapped with a normal relay, the pins are of a different configuration. And the relay is bigger than normal as well.
Sorry, my bad.
I just assumed the relay was a standard 5 pin Delco unit, just like all the ones in the underhood electrical center; that's why I didn't go into electrical diagnositics 101 with Geddy the snowdog. If the relays are indeed different in size and / or shape, then he'll need to do exactly what you suggested.
I'll check my 96 service manual tonight too.
MIKE
