Fuel pump not priming but relay clicks :( (Page 1/1)
ChanningB AUG 23, 02:38 AM
Good morning everyone! Hope all are well! I'm hoping someone can help me with what to do next to troubleshoot the 86 GT i just bought last week... I got it from an older gentleman who decided he just didnt have time to tinker with it any more. When he parked the car a year or so ago, he backed it in his garage under its own power with no issues... car ran great, he was working on trying to give it a show quality paint job. Car sat for a while before he decided to sell vs. finish the paint job ( he had some issues with sanding thru the gel coat and the paint blistered in one place on the hood and in the area above the windshield ). When i went to look at the car, we were able to get it to run with a new battery and starting fluid in the intake... it would run as long as he kept shooting burst of fluid in the intake but died as soon as he stopped spraying fluid. He kept it running long enough to verify good oil pressure, but he said that what he had found was that the fuel pump would not prime for 2 seconds when key is turned on... He said he wasnt sure if it was just a bad relay or if the pump was bad but that it worked fine when he backed in. I brought the car home and started researching here and on the web and found tons of info about testing the relay... had my daughter do key on and off while i held the 2 relays on the firewall behind drivers seat... Key on, clicks... clicks again after 2 seconds. Everything i have read says thats what its supposed to do, so i feel its not the relay.

Where do i go next if the relay is working?... is there a place i can jumper 12 volts off the battery that should make the fuel pump run so i can at least see if it will prime and start the car? I read a lot of post that said drop the fuel tank but the PO told me he had the tank steam cleaned and sealed and new pump installed a few years ago and everything worked beautifully then. Some other things of note for troubleshooting:

-- Door lock fuse removed because PO lost door key and was afraid of locking keys in car (says they work fine with fuse in, says car drove fine with that fuse out)
-- Fuel gauge needle is maxed out full... not sure if it worked before but it is currently maxed out way past full
-- Tach doesnt move or even bump when starter is engaged and held on -- unknown if it worked previously though, so could just be inop
-- The Service Engine Soon light does come on when key is turned on ( I think it might have blinked a couple of times but I'm not sure )
-- Rear deck is removed and the connector for electric latch release is not connected ( pulled this plug on my 88 GT and it still started with no issues, so i dont think that has anything to do with it )
-- I think I have a spare ICM buried somewhere in a spare parts box but i dont have any more dielectric grease to put on it... Is that something that would be worth a try at this point?... or trouble shoot other places first?

I saw a post with a pic of the diagnostic plug that had the far right, upper row connector labeled "fuel pump terminal" , and i thought it was saying i could bypass everything to get the pump to run by applying 12 volts there but was afraid to try it without asking here first... does anyone know if thats right? Can I put 12 volts there with a jumper wire and make the pump run if the pump is good?.. (If not, where is a good place to try it?) The electrical part of cars is not my strong suit and any and all information / recommendations offered is greatly appreciated Thanks so much in advance for any info and advice offered! I look forward to reading your suggestions (Sorry for the long post)

Channing
88 GT - Yellow
86 GT - Red
theogre AUG 23, 08:19 AM
switch ac clutch w/ pump relays to see if connects are bad.

check small connector to tank. is on firewall below bulkhead seal where all wires goes thru. Fuel gauge goes thru it too and gauge peg is likely not connected somewhere.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

sanderson231 AUG 23, 10:50 AM
As Theogre said, check the fuel pump/sender harness connector. It is down low in front of the engine.

If that doesn't work, run a 12V jumper wire to terminal G of the ALDL connector. Remove the trim piece by the cigararette lighter to get to the ALDL. G is closest to the driver's side. This bypasses the fuel pump relay and puts power direct to the fuel pump to run. If it doesn't that likely means the fuel pump is gummed up. That happens a lot if car sit for a long time without Stabil in the gas.

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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged

ChanningB AUG 23, 08:13 PM
Ok, I jumped a wire from the fuel pump slot in the data port beside the cigarette lighter to the battery... I get some tiny little sparks just as the wire touches but no fuel pump priming... I mean nothing... had the wife try to start while I held the wire and it just turns over and over without even a hint of trying to start... what would yall recommend next?

Thanks so much in advance for any and all info and advice 😀
ChanningB AUG 23, 08:24 PM
Ok, test light in the fuel pump terminal comes on nice and bright when I touch the other end to the positive post on the battery.... Should it do that? 😀
sanderson231 AUG 23, 08:27 PM
If the fuel pump is running you can hear a whirr while sitting in the driver's seat. Normally it will run for a couple of seconds if you turn the key to on. You might want to check the resistance to ground on the G terminal to make sure that there is not an open in the wiring. I doubt that this is the case since you got sparks when you tried to jump it. You're probably going to have to drop the tank and replace the fuel pump.

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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged

ChanningB AUG 23, 08:42 PM
Ok, test light probed into dark green/white wire comes on for 2 seconds then turns off when the key is turned on.... that means the relay is good, right? Where can I put the test light to see if power is running to the fuel pump?... Is there any place to probe outside of the gas tank?

BTW, the car started right up for a moment when starting fluid was sprayed in the intake again today so I know I've got spark 😀
theogre AUG 23, 10:12 PM
Put test light aldl G and Ground should light bright when Relay is on.

Find the tank plug as said above. disconnect that. connect test light between tan/wht and blk wires on upper section should do same.
(Pnk wire on same plug the gas gauge.)
ChanningB AUG 24, 07:36 AM
Thank you so much guys!! Connected ground wire to battery, stuck test light in fuel relay terminal, turned key, and light came on bright for 2 secs then turned off. Was able repeat this several times with same outcome. As much as I hate to say it, I think I'm going to have drop the tank.... but I'd rather do that than chase a broken wire any day!

What would yall do next?

Thanks again so much and in advance for yalls input and advice!

Channing
sanderson231 AUG 24, 11:07 AM
Drop the tank to change fuel pump with new suction screen. Also replace fuel filter.

After you get it running check the spark plug for consistent color. If not, pull the fuel injectors and get them cleaned and flow tested. Mr Injector (Bill Johnson) in Idaho is reasonably priced and fast service. He charges $18 per injector. I have experience with partially plugged injectors where it was not obvious from the way the car drove.

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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged