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Fuel pump and relay questions

Old 01-04-2010, 08:26 PM
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Fuel pump and relay questions

So I've been trying to sell the Trans Am as is not running, but it's hard to sell a non running car as you can imagine. So I decided to give it another shot and see if I can't get it running hopefully. I noticed the fuel pump wasn't priming so I started on that path. I jumped 12v to the g port on the fuel pump port on the ALCL and the pump did come on. It primed and when I tried to start it, it did actually come to life for a brief moment. It was the first sign of life I've seen out of it in about a month, so I got a little optimistic. I went and picked up a fuel pump relay and replaced it. Still not working..The pump's still not priming with the new relay, but it will if I bypass the relay.

Any ideas why this is? I wish I had more than an hour of daylight after I get home from work. Thanks.

It's an 86 LB9/Auto btw.
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Old 01-04-2010, 08:54 PM
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Re: Fuel pump and relay questions

OK... first we have to look at what everything does. The prime circuit is to get fuel pressure up so that the engine will fire. The purpose of the relay is to provide the priming power when the ECM calls for it.

Once there is oil pressure, the fuel pump will run even without the relay installed. There is an oil pressure switch that closes to provide power to the fuel pump. Obviously, when the engine is not running, there is no oil pressure, so the relay allows the ECM to prime the fuel pump just so the engine will start initially.

The common denominator is an inline fuse with an orange wire (V6) or an orange wire with a black stripe (V8). This is a 20A fuse that feeds power to both the primer circuit and the fuel pump. From the symptoms you describe, I am guessing that this fuse is blown (most likely cause).
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Old 01-04-2010, 10:11 PM
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Re: Fuel pump and relay questions

Originally Posted by ternandes View Post
OK... first we have to look at what everything does. The prime circuit is to get fuel pressure up so that the engine will fire. The purpose of the relay is to provide the priming power when the ECM calls for it.

Once there is oil pressure, the fuel pump will run even without the relay installed. There is an oil pressure switch that closes to provide power to the fuel pump. Obviously, when the engine is not running, there is no oil pressure, so the relay allows the ECM to prime the fuel pump just so the engine will start initially.

The common denominator is an inline fuse with an orange wire (V6) or an orange wire with a black stripe (V8). This is a 20A fuse that feeds power to both the primer circuit and the fuel pump. From the symptoms you describe, I am guessing that this fuse is blown (most likely cause).
Where would I find the inline fuse you're referring to? Thank you!
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Old 01-04-2010, 10:29 PM
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Re: Fuel pump and relay questions

Between battery and radiator. It's in a 2-wire weather pack fuse holder.
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Old 01-04-2010, 11:15 PM
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Re: Fuel pump and relay questions

sounds like bad wiring, if there was a priming of the pump then there was power. i doubt the fuse is the culprit. i had a similar issue with my lb9 iroc lately turned out to be the distribution point(led from the inline fuse tothe rest of the harness had bad connection with all the other wires) intermintent power try tracing it thought the harness its a pain but i would guess thats you problem.
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Old 01-05-2010, 08:17 AM
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Re: Fuel pump and relay questions

You need to pull the relay out and shoot the power coming into the relay and then the ground that pulls the relay closed. Get a multimeter and shoot for continuity from the ground pin to a chassis ground, I'm guessing the ecm sends the ground to close it. What you really need is a schematic of the starting circuit
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Old 01-05-2010, 10:08 AM
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Re: Fuel pump and relay questions

Turn the key to the on position, if the ses light does not come on then the inline fuse by the battery is blown. It not only supplies the fuel pump, but also the ecm.
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Old 01-05-2010, 05:37 PM
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Re: Fuel pump and relay questions

IT RUNS! Holy Crap! It was that fuse! Thank you guys so much! Sat for a month over a damn fuse, I feel like a moron, but I can live with that right now!
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Old 01-06-2010, 12:37 AM
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Re: Fuel pump and relay questions

Originally Posted by John 89 Formula View Post
Turn the key to the on position, if the ses light does not come on then the inline fuse by the battery is blown. It not only supplies the fuel pump, but also the ecm.
Wrong. The in-line fuse supplies 12 volts to the MAF Power Relay, MAF Burn-off Relay, and the Fuel Pump Relay. The power to the ECM is not connected to this in-line relay (atleast not in my 86 IROC). Also my in-line fuse is mounted on my passenger side fender wall, in between the battery and the tire well.
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Old 01-06-2010, 12:39 AM
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Re: Fuel pump and relay questions

Originally Posted by fast86z28 View Post
IT RUNS! Holy Crap! It was that fuse! Thank you guys so much! Sat for a month over a damn fuse, I feel like a moron, but I can live with that right now!
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Old 01-06-2010, 02:06 PM
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Re: Fuel pump and relay questions

Originally Posted by Chevy86 IROC-Z View Post
Wrong. The in-line fuse supplies 12 volts to the MAF Power Relay, MAF Burn-off Relay, and the Fuel Pump Relay. The power to the ECM is not connected to this in-line relay (atleast not in my 86 IROC). Also my in-line fuse is mounted on my passenger side fender wall, in between the battery and the tire well.
Terminal b1 on the ecm is 12v non switched power, goes right to the in line fuse, there is a junction there with several splices going to different things.

The tpi firebirds' battery is on the drivers side the fuse is mounted on the radiator support
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Old 01-06-2010, 02:14 PM
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Re: Fuel pump and relay questions

FYI, most of these cars have more than one inline fuse, according to schematics. I have had my son's 87 bird completely apart, and his has at least 2 of them.
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Old 01-06-2010, 02:15 PM
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Re: Fuel pump and relay questions

redwhite, the only way he could get the pump to prime was to jump the ALDL connector. Under normal conditions, he said no prime, and no start.
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Old 01-07-2010, 10:53 PM
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Re: Fuel pump and relay questions

Originally Posted by John 89 Formula View Post
Terminal b1 on the ecm is 12v non switched power, goes right to the in line fuse, there is a junction there with several splices going to different things.

The tpi firebirds' battery is on the drivers side the fuse is mounted on the radiator support
Crap!!!!!!! Then the previous owner connected a direct wire with no inline fuse!!!!!!!! I retract my previous statements. Sorry for jumping in the way I did John 89 Formula. If you dont mind me asking, what is the amp size on the fuse for the ECM? Your 86 is an IROC right?
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Old 01-07-2010, 11:04 PM
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Re: Fuel pump and relay questions

What amp is the inline fuse???(5, 10, 20,......)
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Old 01-07-2010, 11:34 PM
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Re: Fuel pump and relay questions

Originally Posted by y84pauloflondon View Post
What amp is the inline fuse???(5, 10, 20,......)
Yeah, in reference to post #11, non-switched 12 volt inline wire for the ECM. Do you know the Amp so that I can install one?
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Old 01-10-2010, 01:32 AM
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Re: Fuel pump and relay questions

i'm troubleshooting the exact same problem in an 89 bird (v6) right now. according to my service manual, the schematic shows a 20a inline fuse powering the fuel pump relay as well as pins B1 and C16 on the ECM. not sure if yours will be the same amperage or not, but i'm really hoping that fuse turns out to be blown when I check tomorrow. until now, I didn't even know it was there. I would love an easy fix...

also...
Originally Posted by Chevy86 IROC-Z View Post
Wrong. The in-line fuse supplies 12 volts to the MAF Power Relay, MAF Burn-off Relay, and the Fuel Pump Relay. The power to the ECM is not connected to this in-line relay (atleast not in my 86 IROC). Also my in-line fuse is mounted on my passenger side fender wall, in between the battery and the tire well.
my schematic shows this as a completely different 25a inline fuse supplying the MAF relay only, so it seems to vary by year. the 89 bird seems to have at least two inline fuses floating around under the hood somewhere, and according to ternandes, it seems the 87 does too.

Last edited by gorbilax; 01-10-2010 at 01:44 AM.
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Old 01-10-2010, 06:49 AM
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Re: Fuel pump and relay questions

My schematics, as well as my experience, put the inline fuse for the fuel pump at 20A.
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Old 01-10-2010, 01:07 PM
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Re: Fuel pump and relay questions

Originally Posted by Chevy86 IROC-Z View Post
Yeah, in reference to post #11, non-switched 12 volt inline wire for the ECM. Do you know the Amp so that I can install one?
20A
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Old 01-10-2010, 01:46 PM
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Re: Fuel pump and relay questions

On my 88' the ECM, MAF, Fuel Pump Switch, Fuel Pump Relay, and Fuel Pump are powered by 20amp Inline Fuse No.2 near the battery.
Don't see why 87', 89' would be much different, if it all.

But,
Vin "E" cars do have separate MAF and Fuel Pump inline fuses.

Last edited by rgarcia63; 01-10-2010 at 06:18 PM. Reason: Additional Info
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Old 01-10-2010, 06:18 PM
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Re: Fuel pump and relay questions

Originally Posted by 86T/A_Ram_Air View Post
20A
Cool bro. thanks.
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Old 01-12-2010, 09:38 AM
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Re: Fuel pump and relay questions

Originally Posted by ternandes View Post
FYI, most of these cars have more than one inline fuse, according to schematics. I have had my son's 87 bird completely apart, and his has at least 2 of them.
You could be right these cars went through a lot of changes over the years.
The one by the battery is the one I'm refering to as it gave me the most trouble.
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Old 01-12-2010, 09:42 AM
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Re: Fuel pump and relay questions

Originally Posted by Chevy86 IROC-Z View Post
Crap!!!!!!! Then the previous owner connected a direct wire with no inline fuse!!!!!!!! I retract my previous statements. Sorry for jumping in the way I did John 89 Formula. If you dont mind me asking, what is the amp size on the fuse for the ECM? Your 86 is an IROC right?
No problem at all.
My 86 was just a Z28 not an IROC but it was tpi.
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Old 01-13-2010, 12:04 AM
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Re: Fuel pump and relay questions

Originally Posted by John 89 Formula View Post
No problem at all.
My 86 was just a Z28 not an IROC but it was tpi.
Just curious, I always wondered what was the difference between the IROC-Z Z28 (mine) and the Z-28. So what is the big difference?
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Old 01-13-2010, 10:45 AM
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Re: Fuel pump and relay questions

it's mostly suspension and steering I think. I'm not exactly sure myself to be honest.
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Old 01-13-2010, 10:57 AM
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Re: Fuel pump and relay questions

on camaros the fuseholder is on the pas side fender next to the battery. on birds it's on the rad support, drivers side next to the battery. the mounting lug is pretty flimsy so if you can't find it, look around for it, it may be lying somewhere with the mounting lug broken off
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Old 01-13-2010, 09:28 PM
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Re: Fuel pump and relay questions

Originally Posted by Twin_Turbo View Post
on camaros the fuseholder is on the pas side fender next to the battery. on birds it's on the rad support, drivers side next to the battery. the mounting lug is pretty flimsy so if you can't find it, look around for it, it may be lying somewhere with the mounting lug broken off

actually on some firebirds it is in the same location as the camaro, just like some cars have 2 MAF power relays and some do not
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Old 01-15-2010, 10:41 PM
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Re: Fuel pump and relay questions

Originally Posted by 86T/A_Ram_Air View Post
actually on some firebirds it is in the same location as the camaro, just like some cars have 2 MAF power relays and some do not
Never heard of 2 MAF sensor relays. I think you mean 1. Mass Air Flow Power Relay and 2. Mass Air Flow Burn-Off Relay.
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Old 01-16-2010, 03:42 PM
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Re: Fuel pump and relay questions

Originally Posted by Chevy86 IROC-Z View Post
Never heard of 2 MAF sensor relays. I think you mean 1. Mass Air Flow Power Relay and 2. Mass Air Flow Burn-Off Relay.

nope some cars havea 2nd power relay on the passenger side of the radiator under the intake. this may be a 85 and 86 exclusive as those are the only two years ive ever seen it on
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Old 01-17-2010, 11:11 PM
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Re: Fuel pump and relay questions

Originally Posted by 86T/A_Ram_Air View Post
nope some cars havea 2nd power relay on the passenger side of the radiator under the intake. this may be a 85 and 86 exclusive as those are the only two years ive ever seen it on
If it's true, then Im suprized. But I do know that some people have utilized these exact relays for other accesories. Did you physically trace the wires to verify if the relay was in fact a 2nd relay for the MAF Sensor?
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Old 01-17-2010, 11:23 PM
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Re: Fuel pump and relay questions

Originally Posted by Chevy86 IROC-Z View Post
If it's true, then Im suprized. But I do know that some people have utilized these exact relays for other accesories. Did you physically trace the wires to verify if the relay was in fact a 2nd relay for the MAF Sensor?

yes sir...i traced the wires from the MAF Power Relay on the fire wall to this other MAF Power Relay on the passenger side of the rad support Rad Support. theres also another relay down there thats much smaller and i don't know what thats for...if i had to guess i would say fans or head light motors since its so close to them. but its definatly there....you can utilize these relays for other things, but i believe they will only work for MAF POWER, MAF BURN OFF and FUEL PUMP because of the plug style
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Old 01-17-2010, 11:47 PM
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Re: Fuel pump and relay questions

True true. but anyone who likes these types of relays can easily order the wiring harness and solder up the wires. If I had the time and money, I would do it. It looks so much better than the old looking box style. So for what year of Camaro did this 2nd MAF relay get installed into?
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Old 01-18-2010, 08:01 AM
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Re: Fuel pump and relay questions

it was a 86 t/a. and this was confirmed by a friend of mine that has cut up alot of totaled out 3rd gens and this relay does exist from the factory in some cars, like i said i think its a 85-86 thing
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Old 01-18-2010, 02:53 PM
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Re: Fuel pump and relay questions

I had a similar issue where I could not hear the pump prime when i turned the key. Luckily , i was at a gas station and not stranded in the middle of nowhere. I pulled the fuel pump fuse under the dash and put it back in. This seemed to reset the signal or something. It started working after that. I have my fingers crossed though, sometimes it will work ok for awhile and stop working again. Seems to me that its an electrical issue in my case. What do you guys think?
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Old 01-18-2010, 03:28 PM
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Re: Fuel pump and relay questions

Has it been running fine SINCE you pulled out and put the fuse back in? Or ahs it continued to give you problems since?
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Old 01-18-2010, 10:32 PM
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Re: Fuel pump and relay questions

yes, the fuel pump has primed every time since (i tried it a few times after i got it home) my guess is that my fuse was not all the way in the block. This would explain intermittent failures. I will post another reply and let you know if it quits working again.
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Old 04-09-2012, 10:06 PM
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Re: Fuel pump and relay questions

Originally Posted by John 89 Formula View Post
Turn the key to the on position, if the ses light does not come on then the inline fuse by the battery is blown. It not only supplies the fuel pump, but also the ecm.
Ha! God Bless This Post!! This fuse is what was keeping my car from running for a week and had hours of my time invested into troubleshooting it!
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Old 08-19-2013, 09:34 AM
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Re: Fuel pump and relay questions

Originally Posted by blackfrontier View Post
Ha! God Bless This Post!! This fuse is what was keeping my car from running for a week and had hours of my time invested into troubleshooting it!
My thoughts excactly! My camaro shutted off while driving today, had to tow it home, only quarter mile luckily. Then all the usual things to find out where the problem was, and at last had to raise hands, I cant find the fault. Then, opened internet and came across with this thread, and all the same sympthoms, run to the car, change fuse, and it starts! So thanks so much guys!!

Last edited by FIN-Z28; 08-19-2013 at 12:10 PM. Reason: typos
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Old 08-21-2013, 03:54 PM
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Re: Fuel pump and relay questions

now I keep extra fuses in the car at all times! :-)
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Old 08-25-2013, 10:07 PM
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Re: Fuel pump and relay questions

What if you turn the key to on position and the ses light DOES come on ?
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Old 08-26-2013, 09:17 PM
  #41  
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Re: Fuel pump and relay questions

you need to pull the engine codes to see what is stored on the computer. might be a good idea to disconnect the battery after getting codes to clear them and reset the computer. Then see if you get the ses light again. There are threads on how to get the codes and what they mean in this forum.
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Old 09-07-2013, 05:36 PM
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Re: Fuel pump and relay questions

hi yall

i have a 1987 trans am gta that i just got outta storage. been sitting for 5 years without starting it. yesterday i went to start it, had a bad battery, but i faintly heard the fuel pump come on. now today, i put in a new battery, turned the key on, and didnt hear the pump come on at all. im baffled as to why the pump aint coming on. any suggestions?



im also trying to locate the fuel pump relay. been lookin on net for a diagram for the relay switch location, but i aint found one yet. any suggestions would be greatly appreciated as i really dont want to have to pay 150 bucks to have this thing towed into a shop and have the tank dropped unless i really have to.

Last edited by transamgta1Khp; 09-07-2013 at 07:09 PM.
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Old 09-07-2013, 10:47 PM
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Re: Fuel pump and relay questions

fuel pump relay is one of three relays usually on the driverside firewall
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Old 09-07-2013, 10:49 PM
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Re: Fuel pump and relay questions

I think its the middle one. Left is burn off relay and right is MAF relay?
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Old 09-08-2013, 12:55 AM
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Re: Fuel pump and relay questions

I would not go by "it may be here or there." That can be misleading in some cases. Better yet, why don't you say the 4 wire relay is in the middle and the other relay with blah blah blah colored wire is on the right and the other relay with the blah blah blah color wire is on the left. That would clear up ALL confusions. Cool guys. It ain't that hard to figure things out.
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Old 09-08-2013, 12:57 AM
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Re: Fuel pump and relay questions

Come on*
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Old 09-08-2013, 07:00 AM
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Re: Fuel pump and relay questions

Originally Posted by Chevy86 IROC-Z View Post
I would not go by "it may be here or there." That can be misleading in some cases. Better yet, why don't you say the 4 wire relay is in the middle and the other relay with blah blah blah colored wire is on the right and the other relay with the blah blah blah color wire is on the left. That would clear up ALL confusions. Cool guys. It ain't that hard to figure things out.
The middle one is the MAF relay. It's labeled, but the other 2 I'm not sure of. I unplug the battery, & I hear the middle one click. No sound from the other 2. Does the MAF relay work the fuel pump?


i can post a pic of the 3 relays if yall like. but middle one is definately the MAF sensor.



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Last edited by transamgta1Khp; 09-08-2013 at 08:20 AM.
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Old 09-08-2013, 08:20 AM
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Re: Fuel pump and relay questions

figured id add the pic so no guess work
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Old 09-08-2013, 10:33 AM
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Re: Fuel pump and relay questions

Originally Posted by Chevy86 IROC-Z View Post
I would not go by "it may be here or there." That can be misleading in some cases. Better yet, why don't you say the 4 wire relay is in the middle and the other relay with blah blah blah colored wire is on the right and the other relay with the blah blah blah color wire is on the left. That would clear up ALL confusions. Cool guys. It ain't that hard to figure things out.
Could you possibly be any more rude?! I work like 12-14 hours a day selling cars, and in between a flux of people find the time to help point somebody in the right direction while running around at work and you have to be a jerk because it wasnt specific enough? I'm not sitting on my butt at home with plenty of time to research these things.
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Old 09-09-2013, 01:29 AM
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Re: Fuel pump and relay questions

Originally Posted by blackfrontier View Post
Could you possibly be any more rude?! I work like 12-14 hours a day selling cars, and in between a flux of people find the time to help point somebody in the right direction while running around at work and you have to be a jerk because it wasnt specific enough? I'm not sitting on my butt at home with plenty of time to research these things.
I wasn't being rude. I was just stating that anyone can easily give a better discription of the issue at hand. Might I add, I wake up at 3:15 am to work at a warehouse. When I get out at 12:30 pm, I either go to my second job as a computer repair technician or I go to my local college. If not that, I'm driving around my county picking up and delivering computers because I run my own home business as a PC repair technician, and I'm licensed by both state and city for "electronics repair." So your not the only one with a full plate man. But like I said, I'm not here to argue. I hope that everyone here can give a better discription of an issue so that we all can help each other out. If you got offended, I apologize.

Now down to the nitty gritty

MAF relay has the following colored wires = orange, blue, tan/white, black/white, and red. (5 wires)

MAF Burn-Off Relay has = tan/white, black/white, green/white, red OR orange (not sure of the color), and orange. (5 wires)

Fuel pump relay = blue, black, orange, orange (4 wires)
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