Ok, going to try and make this is informational as possible so that it can be addressed immediately. Had this car (1988 Firebird 305 TBI/WC T5) for a couple months, since i got it we needed to crank it long enough to build up oil pressure to engage the fuel pump to get it to start, it would smoke a little and stumble for a bit but would get over it and level out. When i first started it up it threw a code of something with the fuel system. Can't remember the code number but it said fuel pump relay on my reader, replaced it, did the same thing. I ended up returning it. Ended up replaceing the fuel pump, replacing 99% of the line going up to the TBI, replaced the fuel pump (original delco with 140k+ and still probably was good for more), rebuilt the TBI.

Anyways, i've narrowed part of the problem on the fact that it doesn't prime anymore, i swear it used to but it doesn't now.

As far as the fuel pump relay i've done as much research as this site has provided me and the haynes manual is f***ing useless. Anyways, Battery is hooked up, getting 12.95 volts, i test the fuse by the battery, still good, go to the fuel pump plug, test the orange and black on the plug, i get 12.95, and i test the orange with grounding it elsewhere on the car, still 12.95, so main power is not the problem. All fuses inside the car are brand new and check out when tested.

I test the red wire, 0 V with ignition off, steady 5.7 mV once ignition is turned on.

I test the green/white wire (informed elsewhere this is the prime wire), .01 mV when off, 106.7 mV for approximately 1 second once ignition is turned on, steady 71 mV after that. Turn the ignition off and you get 4.5 mV for approximately 4 seconds, and then after that it goes back to a steady .01 mV.

I then took the relay, and bench tested it, hooked up the Digital volt meter, hooking up a 12.12 V source to the orange wire, grounding it out with the black wire. Grounded out the digital volt meter with the black wire, stuck the positive side of the meter on the tan wire. Then connected the green/white wire to the 12V source and yeilded a 11.71 V connection going through the tan wire and it clicked as it should. My assumption is either the power sharing of orange and green or just how the relay works is the only reason for the .4V drop, but needless to say with a normal operating system in the car running at ~13V - 14V, worst case is 12.6V getting to the tan wire of the relay, so more or less 12 by the time you get to the pump (not physically tested, just a hypothetical statement). So the relay doesn't seem to me to be the problem. Car will start up once pressure is built, so oil pressure sensor has been ruled out.

I'm leaning towards either a wire problem, i just down loaded a wiring diagram of the ECM, so i will be testing terminals of the ECM to see what happens when i turn them on to see if there is a problem with the wiring inbetween there and the relay. My worry is that it's the ECM, of which leads me to a question that might be able to be answered right away. I have 3 ECMs, all from 2.8L V6 MPFI cars, 86, 87, and an 88. Is it possible that if the ECM is bad that i can use one of these ECMs and just swap the chip??? Otherwise is it alright to take an 88 305 TBI automatic and switch the chip into that ECM so i don't have the auto/manual issues?

Sorry this is so long but i'm just trying to do as much testing now as possible so that i can get quick results, i'm going out of town on friday, and while there i'm going to a junk yard so thats why i need to know what i need if i do actually need something. Thanks for any help!

Jon

 

using this as my reference as the haynes manual i have doesn't even cover TBI in the wiring section.

http://www.austinthirdgen.org/mkport...ine_wiring.gif

this doesn't seem to be complete as it looks like there should be more connections to the ECU on the right side, and has me wondering about credibility as if you look towards the middle on top, in reference to the fuel pump relay, it goes down to the ECU, says dark green/white, then goes into terminal A11. if you look on the bottom row, more towards the left, 4 in, there is A11 again refering to a black wire going to what looks like to be the coolant temperature sensor/intake air temp sensor/throttle position sensor/manifold absolute pressure sensor.

I don't know has me curious, but i went down and tested what i could figure out on the ecu. Looked at it and terminal 1 on plug A is an identical thickness and identical dark green with white stripe on the relay, seems to be the only one on the wiring harnesses, but anyways, i tested B1's orange wire and got battery voltage so i knew power was going into the ECU. Turned the ignition on and A1 (dk green/white) stayed at battery voltage with the ignition on even after 2 seconds (priming?). Can anyone confirm this is the right wire i'm even testing, and that it should maintain battery voltage and not go out in 2 seconds...what trips it into doing just two seconds?

All in all it may just be a typo in the picture, A11 in reference to the fuel pump relay when it's supposed to be A1, considering on my harness A11 is actually black, which would make me think it's for the coolant temp sensor, ect as mentioned above, as it would match the wiring diagram's second A11 reference. But for documental and reference purposes you think it would have been double checked. Any insight is appreciated, thank you!

 

84redta

Yes, it is a typo. A11 is a sensor return pin (aka ground)

ECM Pin A1 is a pin which control Fuel Pump Relay - dark green-white. Inside engine compartment, on the drivers side near PS booster look for relay which has dark green-white (16 AWG) and black-white wire (16 AWG). This socket should also have pink-black, red and orange color wires - the later should be 12 or 10AWG sized wires. Orange is is always hot goes to battery, pink-black (sometimes this wire is gray) goes to FP in the gas tank. Red wire either goes to pin G of ALDL or hangs loose to a pig tail spade connector. The later is used as FP test node.

Pull relay from its socket - take good look at contacts. If you see discoloration you'll have to replace socket. Just replacing relay and cleaning contacts is a short term solution. Contact oxidation is very typical in east coast cars due to moisture and road salt.
ECM should power FP for about 2 seconds during POST .

//RF

 

I thank you for reading my book. My appologies there.

As far as the typo, thats what i assumed, as A1 was the only dark green/white stripe wire there. When ignition is off i get 0V, and once i turn the key into the on position, i get it a solid battery voltage, it DOES NOT turn off after two seconds which confused me.

I have in order from left to right, orange, red (looks orangish from age), dark green/white stripe, black (maybe white stripe, can't remember), and then tan/white stripe that goes to the pump.

I tested all 12V sources going into the ECM and all checked out appropriately so i know it's getting power, i haven't checked grounds on the ECM but as mentioned the dark green/white stripe wire in A1 does have a constant ~12V when the car is turned on. So i get ~12V at the ECM, but i get 107 mV at the connector, so either the wire or the connector are the culprit at this point.

What is the red wire??? Is that like a ground switch that would shut that 12V off after two seconds??? I can't find anything on the red wire and if you look at the wiring diagram i posted above it calls it a "Fuel Pump Prime Connector." I thank you very much RF!!!

Jon

 

im having sort of the same problem. when i ump the orange and grey in my 91 rs, sometimes i get the pump tp prime and sometime it doesnt. would the oil pressure switch also cause the pump not top prime?

 

tony, from my understanding if the oil pressure switch is bad it would have your fuel pump running 24/7 reguardless of if the key is in the ignition or not. Many people notice this issue when they go to start thier cars in the morning to find them dead because the pump killed the battery from running all night.

I started the car today, a lot smoother so either me fixing the fuel lines or replacing the pump helped significantly, got a code 54 and a code 15. Code 15 i'm assuming is the fan switch on the passenger head??? As i know that is bad and i have to crawl underneath to replace it, but either that i know the harness plug for the coolant temperature sensor is a problem area with east coast oxidation.

Code 54 i'm guessing is the problem that i'm not getting 12V to my fuel pump relay via the green wire, so i'm going down to check the harness plug. Anything else i should be checking with these codes please let me know! Thanks.

 

im pretty sure the fuel pump is bad, but im just checking everything over just in case. the problem now is when i turn on the ignition, my ses light doesnt come on. i had it on once and running then it died. no ses light after that. i know it works but i cant check codes. the fuel pump still doesnt prime either. now im stumped...

 

my suggestion for you is to check all fuel lines, main 3/8" feed line and the return line, make sure that there is no crimping, leaks, anything of that nature, replace the fuel filter if you haven't already ($7...c'mon ), and then get a fuel pressure testing guage for TBI and test the fuel pressure, i think mine was alright and i dropped all the bars and now i gotta hope that i can get two bolts out that the heads broke off of so that i can re-thread and put the back end together. If you go to replace the fuel filter and what dribbles out is rusty or gritty, then i would suggest dropping the tank anyways as replaceing just the filter isn't going to help the issue, it's just going to be a temporary bandaide.

https://www.thirdgen.org/forums/v6/1...hlight=code+54

i found this today, it is a great resource to checking your entire fuel system. Maybe it might be able to save you some time. Good luck!


Back to my issue, can anyone tell me what the "red" wire that is inbetween orange and dr green/white stripe wires? Where does it go? Just trying to figure it out, i'm pretty sure the ECU is good, the wiring is bad, but i have to do a little more diagnostics.

 

84redta

The red wire is a fuel pump test wire. To test fuel pump without ignition connect a fused +12 volt to red pig tail wire. This will power up fuel pump instantly. From your testing it appears that your FP relay source line dark-green/white is broken. My guess that it is probably right inside connector, at the connector crimp.

Remove FP relay from socket, turn ign into run position, but do not start engine.

photo of bad FP socket, FP relay is removed, upside-down on a spool of electrical tape:






locate pin that corresponds to dark-green/white wire (one of the two small spade plugs) measure voltage with respect to ground. Wiggle dark-green/white wire while measuring voltage if pops time to replace contact pin inside connector.

The reason why you get constant + 12 on A1 is that during POST ECM is monitoring FP voltage at ECM pin B2. If it sees +12 volt (pump is priming) it will shut it off after two seconds (end of POST). If FP relay fails, ECM keeps A1 line at +12 and code 54 is set..

You FP socket - relay maybe different!

POST = Power On Self Test


//RF

 

RF...what is that relay??? i look up the fuel pump relay and i get the rectangle one...not this round one...but mine looks identical to yours!! Pics to show...from the picture, clockwise...burnt is big black/red stripe, then green/white stripe, then red (battery voltage going to that), and then beige white.

I jumped red to the tan/white and got a humming in the engine compartment...not the fuel pump i don't believe...when i jump the orange wire with the tan/white stripe wire of the rectangle relay i get the humming of the fuel pump and can clearly hear the fuel making it's way around the system. Please inform me of what i should do and what relay am i looking for as when i look up fuel pump relay i keep getting the rectangle one pictured below. The oval burnt relay i got has this on the top of it...assuming part number?? "5319 / 14089936" then a pic of the curcuit inside. Any help is appreciated!! Can't believe i didn't think to check out this relay from the start...

Jon

 

Let me see if I have a square looking relay

 

rectangle...approximately 1" X 2" maybe? Shown in pic 3

The rectangle relay had from left to right, orange (constant 12V), red (?????), dark green/white stripe (thought it was primer, but at this point i don't know...), black (ground), tan/white stripe (fuel pump). You energize the tan/white stripe with orange and you hear in the rear of the car the pump turn on and pump the fuel system with gas.

My oval one is from burnt one clockwise black/red stripe (ground), green/white stripe (A1 on ECM???), Red (constant 12V), and beige/white stripe (jump that with red and i get a tiny hum from engine compartment...not fuel pump)

 

If you look at your FP relay it is SPDT relay i.e. single pole double throw. Center contact is connected to FP wire tan-white, red wire is connected to NC (normally closed) set of contacts - this is why it is used to test FP (with relay installed in the socket).

When ECM applies +12 to relay - relay responds by moving contact from NC to NO position making connection between tan-white and orange wire. Orange wire is your always hot battery. Whola - fuel pump is on.

Can you take a photo - wife is calling for dinner!
//RF

 

look above, i added photos So whats the name of this oval relay in my case??? I don't understand why when i look up fuel pump relay online it gives me the rectangle relay pictured above but this oval one is clearly burnt and potentially not grounding out properly as thats what terminal burnt.

Also i am checking wiring diagrams i have available and have found for my application and it isn't showing this relay anywhere. I thought i read that there is an A/C relay right there too...but my a/c works as far as i know??? Almost all the colors correspond though with the fuel pump wiring colors except for the big black/white stripe (which i have on the rectangle relay) wire on the diagram i got a black/red stripe (on the oval relay) and i don't have a 5th wire as pictured in the schematic i attatched in post #2 anywhere on my second relay...i'm confused now...thank you for your help and if you need to eat by all means enjoy!

 

hey rf...i'm looking at partsamerica.com and checking out "relay." The relay i'm holding i think is my radiator fan control relay. Sound about right?? I don't have a wiring diagram to check. Checked it again, all it does is whine when 12V is jumped to the tan/white stripe and it's a little louder on the driver side...don't know what it's feeding w/out tracing wires. If this relay was bad could this be why my radiator fan doesn't turn on unless the a/c is on, or would it still be combined with a potentially bad radiator fan switch? Or can this be my code 15???

Still leaves me the problem of no priming at the fuel pump relay though. I believe that the rectangle is my fuel pump relay as it matches the wiring diagram in post #2 identically. There is no sign of wear or any burntness.

 

OK You should have two relays next PS booster. One is used for FP and the other is used for AC circuit.

Fuel Pump relay should have:

dark-green/white stripe wire
black-white wire
Orange
Tan-gray to fuel pump
optionally red pig tail

The oval relay I think is used for AC circuit.

green/white
tan/white
Red
Black/red

//RF

 

ok yup, i found a wiring schematic for a VIN E for a 92 for the radiator fan system, and went down after figuring out what the wires were, connected the black/red and the red and it turned on my radiator fan. Since the way the system grounds is if you have the a/c on in the car or the fan switch kicks the relay...since the only way i can get my fan to work is to turn on the a/c then i'm assuming the relay works despite the marring and burning of the relay plug although that plug is probably on it's way out.

Apparently the "hi" curcuit of the a/c system uses the same relay (or just same part number relay)...maybe all in the same, reguardless we've narrowed it down to my fuel pump relay is the 1"X2" rectangle relay...

Since i have 12V at A1 on the ECM...if i was to run a new wire to the fuel pump relay and connect it 6" down on the relay plug (green to green obviously), and it kicked the 12V to flip the switch in the fuel pump relay...theoretically if i understand this correctly the tan/white wire that goes to the fuel pump will also feed B2 on the ECM and activate the POST and the 2 second count down? Solving my "Small voltage in B2 within 1.5 seconds" problem? Just trying to figure it all out in my head. Thanks again for your time!

 

No problem.... Glad to be of help. Post more Q's.... BTW I used to live in Smithtown LI back in the late nineties.... Now I am back in Cal

//RF

 

yea i've been to Smithtown a couple of times, nice place, wouldn't mind cali though except those blasted emissions. I'm not one to let my car get away from me emissions wise. Yet still a pain.

Anywhere you would look for a break or problem areas for this green wire. I swear my car used to prime and thats why the code 54 went away for the longest time...but since my car has sat for maybe 1-2 months without being started, i rebuilt the whole fuel system damn near, and magically the code 54 pops back up. Why would it do such a thing???

Any insight to area's to check would be great...otherwise i'm just going to get new green wire and butt connect it inside the passenger side of the car, run it out of the car, through the looms and over to the fuel pump relay and like i said just go 6" down and butt connect with some heat shrink wrap or something.

Also any idea on what size guage wire would be safe for this?

 

Check relay connector first- find that dark green/white stripe wire. Poke into it - see if you get +12 Volts. Also, check and see if ECM side pin is seated fully.

Use 16 or 14 AWG multi stranded SXL rated wire - it is specifically designed for automotive primary wire and can be used in engine compartments where higher heat resistance is required according to SAE J-1128. Do not use stuff from HD or local hardware store. That stuff will melt eventually and leave you stranded somewhere on side of LIE.

I get my spools from Waytek
http://www.waytekwire.com/automotive-wire.htm

You local autoparts store may have small spools of this stuff.

//RF