Here is the problem. I have 12v at the battery, 12v going to the fuel pump relay at the harness, but only 7v at the fuel pump connector. What to do now? As far as I know, the pump does need to run off 12v correct? I can hear the relay come on and go off. What could be going on? Thanks for your help.

-Buck

I moved this here in hopes of a better response. It was in Electronics. Thanks

 

Correct; try running a new line back to the fuel pump and see what happens.

 

Okay, i thought about that, and i dont want to sound like an idiot, but exactly how, cause i do not want to burn my pump up by hooking a 12v lead to the ground or to the signal wire ( i think that is what it is called). So i will say that the plug looking at it, the first wire is #1 is on the driver side and #2 is the middle and #3 is passanger side. Which one to hook the 12v lead to. Or will i have to connect a ground and a 12v to complete the circuit, or will all three need to be hooked up? My Haynes book shows nothing about the plug for the fuel pump, even in the revisions section. Thanks

-Buck

 

I would first throw on a new relay. It may be working, but the contacts are dirty, not allowing full voltage.

Then tryin running another wire. Possibly one size bigger then stock.

If that doesnt work, try creating a whole new aftermarket relay system tapping strait off the battery.

 

When i was testing it i jumped A and D on the wiring harness and still nothing happened. I am going to try to connect a 12v lead to the G on the ALCL and see what happens there, but i am expecting nothing because the voltage is just not getting back to the pump.

-Buck

 

I like Dale's suggestion better. Wait- you asked for the wire; didn't you say you saw 7volts at the fuel pump connector already? Should be the same wire, then!

But since I'm such a swell guy, here's the code 54 chart that I typed up for someone a long time ago. I believe you want to go towards step "1A"- but maybe you want to run thru the whole chart. Step 1A is the only section that deals with the connection at the rear of the car.

(You could've found this too, with a <a href="search.php?s="><img src="images/top_search.gif" alt="Search" border="0"></a> on the V6 forum for "code chart fuel")

.................................................................................................

-----------------------------------------------
DIAGNOSTIC CHART FOR CODE 54 (2.8L MPFI ENGINE)
---------------------------typed by Tom P------

Preliminary stuff:

Ignition off for ten seconds.
Ignition ON, listen for in-tank fuel pump
Fuel pump should run for 2 seconds after ignition on

Not ok? See "1"
Okay? See "6"



1. Ignition off. Remove the fuel pump relay, but keep the harness connected. This is
____located on the top of firewall, driver's side, on a relay bracket. It's the leftmost
____relay, with a connector that has these wires: Tan/white, black/white, green/white,
____orange, orange.

____With the relay still connected, back-probe terminal "A" (that's tan/white, circuit
____CKT #120) with a test light to ground, make sure you can see the test light from the
____driver's seat. Turn the Ignition to on (don't crank the engine/start the car). The
____light should turn on within 2 seconds.

____Light on? See "1A".
____Light off? See "2".

___1A: Repeat the test on CKT 120 (tan/white) at the rear body connector. You saw this
________connector if you replaced the fuel pump, it's in front of the tank, against the
________top of the underside of the car.

________Light on? Faulty pump ground or pump (ouch!)
________Light off? Fix the open (break) in circuit 120.



2. Disconnect the pump relay. Put the ignition on, engine stopped. Probe the fuel pump
____harness connector, terminal "E" (orange on the edge of the connector, Circuit 340)
____with a test light to ground.

____Light off? See "2A"
____Light on? See "3".

___2A: Repair open in CKT 340, this comes off of both your "computer-and-oil-pressure-
________safety-switch" setup and your "fuel-pump-and-computer-fuse".

________Your fuel pump/ECM fuse is under your hood, screwed down to the upper-frame-rail
________on the passenger side of the car, close to the air cleaner & black fuel-vapor-can.
________You'll see two little black boxes, each with two wires coming out of them, screwed
________down to the upper frame rail by one screw each. One of them has a red wire and an
________ORANGE wire coming out of it- that's your pump/ECM fuse holder. Pop the top off
________to see the fuse. (The holder with red & brown wires is for your 85-89 MAF sensor.)

________Now, two things could happen here. You could have a bad fuel pump fuse- check the
________fuse. If it looks okay, replace it anyway... sometimes a fuse can look good, but
________really be blown. The second possibility- I want you to probe the red wire on the
________fuse holder with a test light to ground. The red wire goes to the positive-
________junction-block on the radiator support- your pump/ECM fuse might not be getting
________any power! If the light doesn't light, check the red wire hookup. However, with
________either case your computer would be acting up, too, and I don't think you could get
________the car to start at all.



3. Connect a test light beteween pump connector pin "B" (black/white wire, CKT450) and
____pin "E" (orange wire from step 2, CKT340).

____Light off? See "3A"
____Light on? See "4"

___3A: Repair open CKT 340. The black/white wire isn't making a good ground. Sorry, I
________don't know where this grounds out to. I'd imagine it goes to a screw on the car.



4. Connect test light between pump connector terminal "C" (dk green/white wire, CKT 465)
____and ground. Ignition to "off" for 10 seconds. Note test light within 2 seconds after
____ignition "on".

____Light on? See "4A"
____Light off? See "5"

___4A: Faulty Relay! Hey that's cool, a $10-$15 part from the GM dealer! But, if you
________replaced that already, something's funny. You might want to do the chart again.
________Check for intermittant connections, possibly caused by dirty connector contacts.
________Note: The manual continues to test the "oil pressure safety switch", I'll put
________that test at the end of this message.



5. Ignition "off". Disconnect ECM A-B connector and check for an open, or a short to
____ground, in circuit 465- that's the dark green/white wire from the relay. It's on
____terminal "A1" of the ECM A-B connector.

____CKT 465 okay? See "5A"
____CKT 465 Bad? See "5B"

___5A: Check resistance across pump relay pins "opposite harness connector terminals B
________and C". Should measure 20 ohms or more to be good.
___________Resistance good? Faulty ECM A-1 connector, or bad ECM
___________Resistance bad? Replace Relay AND ECM.


___5B: Fix CKT 465. If CKT 465 was shorted to ground, re-check for a light "on"
________between harness connector terminal "C" and ground within 2 seconds after ignition
________"on".
___________Get a light? Cool, reconnect your relay
___________No light? Faulty ECM terminal "A1", or bad ECM.



6. Clear codes. Start engine and note service engine soon light. If the light comes
____on, check the code, if it's not 54 or you don't get a light, it's something else
____wrong, or an "intermittant" problem.



7. Backprobe ECM terminal "B2" (that's tan/white, CKT 120) with a test light to ground.
____Ignition off for 10 seconds. Note light within 2 seconds after ignition on.

____Light on? See 7A
____Light off? See 7B

___7A: Faulty ECM terminal "B2" or bad ECM.
___7B: Repair open circuit 120 to ECM terminal "B2".



*** Oil pressure switch test: Our 2.8's have two oil pressure switches. One is for the
gauge panel to control our oil pressure light (or gauge). The other one will keep the fuel
pump running if the relay happens to die while you're driving. I assume the theory was that
if you pull out onto a highway and the relay dies, you don't get killed? Contrary to popular
belief, this switch does NOT turn the pump off if oil pressure goes to zero. That's false,
and can easily be seen by looking at the f-body's wiring diagrams. Anyway...

OP1. Start the engine, get it up to normal operating temperature. If you can, verify that
______the oil pressure is normal. Disconnect fuel pump relay- the motor should keep running.

______Engine stops? Bad oil pressure switch.
______Engine keeps going? See "OP2"

OP2. Reconnect fuel pump relay. Ignition "off". Find the fuel pump test terminal on the
______ALDL (Assembly Line Diagnostic Link, the connector above the driver's feet you used
______to get the error code out), which is terminal "G" -- the bottom leftmost terminal.
______Probe that terminal "G" with a test light to ground.

______Light off? No trouble found! (Doubtful, if you got this far & nothing's wrong...)
______Light on? Bad oil pressure switch. Oh yeah this switch is screwed into your engine
_________________block, right above your oil filter, with an orange and a tan/white wiring
_________________harness on it.



Whew.

-Tom P (Hot rodded 1986 Firebird 2.8l)

 

Thanks for the info. Okay now if i have to replace my fuel pump do yall reccomend that also install a PULSATOR and a STRAINER. i already have a new filter to put on.

-Buck

 

Do a search for pulsator with the username TomP and you'll find your answer for that (there's a current thread with info from TomP on the pulsator).

You should purchase a new strainer.

As far as the voltage issue goes, I agree with Dale. First try a new relay. That is the most likely cause of the problem. Second, try testing the resistance of the +ve wire that runs from the relay to the rear connector; you can do this as follows:

1. Get a length of copper wire about as long as the car and measure its resistance. It should be close to zero ohms.
2. Hook this wire to the wire at the relay that runs to the rear connector.
3. Take the other end of the wire, get under the rear of the car, and measure the resistance between the dangling wire you've just added and the correct terminal on the rear connector.
4. Subtract the original resistance (if there was any) from this resistance.
5. If this produces a large resistance (compared to the copper wire you measured originally), that wire is your problem.

Hope this is clear.

 

Here are the results of this chart. I was not able to get under the car last night to check #1A, but in doing all the other steps #4A says that i have a bad relay, but i am not sure so i am going to buy a relay today anyway and see if that fixes the problem. Thanks for the help.

-Buck

4. Connect test light between pump connector terminal "C" (dk green/white wire, CKT 465)
____and ground. Ignition to "off" for 10 seconds. Note test light within 2 seconds after
____ignition "on".

____Light on? See "4A"
____Light off? See "5"

___4A: Faulty Relay! Hey that's cool, a $10-$15 part from the GM dealer! But, if you
________replaced that already, something's funny. You might want to do the chart again.
________Check for intermittant connections, possibly caused by dirty connector contacts.
________Note: The manual continues to test the "oil pressure safety switch", I'll put
________that test at the end of this message.

 

So for step #1, you got "light on", and then the chart was pointing you towards step 1A? Gotta do step 1A then, because that's where your problem is.

Also, I'm curious, where did you measure the 7 volts from? Was this with the engine running, or with the engine stopped but the key on?

 

I have just set this engine in after a fresh rebuild, you know new pistons and bored and what not. Anyway this car has set since 96 and i am bringing it back to life. I have not been able to crank it yet because i cant get the fuel pump up and going to drain the tank and put new gas in and crank it. So all the test i do, the engine is off, but the key is on. The 7 volts was measued between #1 and #2 and #2 and #3. both of these measured the 7 volts.

I also posted another question about the A and D but to energize the fuel pump is the relay connected or not? And no it wasnt in the chart this was in the Haynes book and it never said anything about the relay having to be connected or disconnected to energize the pump. This is a PITA after all I have done so far. Everything on this car has had to be replaced. Thanks for help.

-Buck

 

Okay, cool! The pump relay is only useful when the engine isn't running. As soon as the engine starts running, the oil pressure switch supplies +12 to the pump, not the relay. So you're right by looking at the relay. When you say you got 7 volts between #1+#2, and #2+#3, you mean the fuel pump connector at the back of the car, right?

I'll have to look at my Haynes book when I get home; but the chart I gave you is directly from the GM Service Manual. I'd trust that a LOT more than I'd trust the Haynes book. I'm not near my GM manual right now, so I don't have a wiring diagram to tell me what terminal A/B/C/D/E mean on the relay.

(I have the GM Service Manual from http://www.helminc.com and the Haynes book; I really like Haynes for basic mechanical work- change rear axle, caliper rebuilds, drop fuel tank, suspension rebuild, etc, but NEVER for diagnostic work.)

So I'm still not sure about your results from step 1?

Did it tell you to go to step 1A?

If it told you to go directly to step #2, you don't have to do step 1A at all, and like you said, it's probably the relay- or corrosion on the relay's contacts.

 

The chart did say to go to step 1A but i had no help last night and it is doubtful that i will tonight also. So i am leaving work and going home right now, so i am going to stop by Auto Zone and buy a relay and then i will let you know what comes of it in the morning. You have been a great help. And yes the volts was from the connector in the back just like you said. So if that other book tells you to try something differnet than i already have let me know. Thanks again!!!

-Buck

 

Well the relay did not fix the problem, so it has to be a bad ground to the pump or the pump itself. Any idea where the ground is to the fuel pump? Also does the harness for the fuel pump run under the carpet? Reason i ask is when i got this car 2 years ago, like i said it had been sitting since 96 and it had no driver side window for about 2 years ( had to get water out from under the carpet ) and if the harness does run under the carpet then maybe that is where it grounds to the body and just maybe it is rusted up. Let me know what you think.

-Buck

 

yes, harness runs on the cab floor, and thru a junction in the back middle, behind the rear seat.

 

I think i am going to pull the carpet just to make sure that the wires are okay from there to the ECM or relay, or where ever they go from the fuel pump. Before i drop the tank. Thanks

 

Start back by the tank and work forward. Pull back seat and that carpet, then work down to rocker panels, etc.

 

Would you happen to know what side the harness for the fuel pump runs down? That way i know which seat to remove. Thanks

-Buck

 

I cant remember that for 100%, but I think drivers side. Thats why I said start at the back seat, and work forward.

 

Well, if the chart said to go to 1A, then that's where your problem is. You've either got a faulty pump ground or pump (both suck, cuz ya gotta drop the tank), or a short in circuit 120. I hope it's just a short! Seems like it. When you checked voltage at the back of the car, did you disconnect the fuel pump connector? Or did you just backprobe the connector? Unhook the connector and then check voltage. Hopefully it's 7 volts, and it's just a short.

Yes, the wires run down the driver's side. Try running a new wire first before you go in depth!! A GM mechanic wouldn't spend the time to find a short; they'd just run a new wire.

Oh heck since I'm home... lets check out the Haynes for A&D... okay, I can't find it. Got a page # or a chapter/section # for where you read that about jumping A&D?

 

Alright update since my last post. I have dropped the tank and it was not as bad as i thought. Anyway good thing i have dropped it cause all that gas that has been sitting in the tank since 96 has clogged up the return line, ate the rubber off the pump, ate the pulsator up and clogged the strainer. Not to mention the junk in the bottom of that tank and the smell was awful. So i am going to replace the pulsator with a hose, replace filter and buy a new pump and strainer. Also blow all the lines out with some compressed air. Any suggestions for things to do while the rear end and tank is out of the car? Thanks

-Buck

 

Check for any rust, and put some POR-15 up there. Replace all of the bushings with polyurethane components. If $$$$ is no object, upgrade the rear to a posi and rear disc brakes.

 

What is POR-15? And have no cash for anything else right now, but these rear ends come out with no problem, so what you are suggesting is in the works for the middle of next year along with sub-frame connectors, drop springs, new shocks, strut tower brace, and IROC-Z wheels, etc. And when i race other pepole i might not get them in the straights but the curves they will have no chance. Anyway wishful thinking but thanks.

-Buck

 

Okay, it is between the Master fuel pump or the Carter. The Master comes with nothing, and the Carter comes with everything, there is a 20.00 dollar difference. So the total price for the Master pump and the straner is 60.97 and the Carter is 80.55. Any suggestions?

-Buck

 

Or is a fuel pump to relace stock just that, a stock replacement. Nothing special. Let me know what yall think.

-Buck

 

Anybody have anything to say? I guess i am going to buy the Carter if there are no objections. Thanks

-Buck

 

I'm pretty certain that the fuel pump I put in is a Carter. I haven't had any problems with my car so far... at least not any problems that I could definitely blame on the fuel pump.

Do a search on fuel pumps in the V6 forum, try searching for Corvette fuel pumps because I think that might a popular replacement. Perhaps vsixtoy has a suggestion since he goes for the best on everything.

 

Hey TomP:

Would you install a new pulsator or not. I have read other post and you are for it if you have it and if not then just run a high pressure hose. Which do you recommend highest? Thanks

-Buck

 

I'm gonna guess what TomP's answer will be. Go for the pulsator if you feel like spending the money and think it might reduce noise. Otherwise go with the hose.

 

If i buy the Carter it comes with everything for 80.55 and the Master does not. So i am going to buy the Carter this evening. Thanks

-Buck

 

CJ wins!!

The big point here is NOT to re-use the old pulsator. The new pump should come with a short length of high pressure hose, you'll just need to get clamps. (I used little clamps labeled "fuel injection clamps", seems like they provided a 360 degree seal instead of a usual small hose clamp, I think it was $3 for a carded package of 4?)

Good thing you found that messed up pump -and- the bad gas before running your brand new motor... wow. As to pumps, you might want to consider an AC/Delco... I'm on my 2nd borg-warner piece-o-crap pump. First one died for no reason. Now this second one has a broken anti-drain-back valve. My next pump will be genuine AC/Delco!! That original pump lasted me up to 1996.. 10 years since the car was built; how am I on my 2nd pump in 8 years? Ugh.

Plus, you could ask (or do a <a href="search.php?s="><img src="images/top_search.gif" alt="Search" border="0"></a>) on the "TPI forum" for more opinions. Or maybe instead, put up a message on the General Tech forum- it gets more traffic- and ask for opinions about pumps. But an AC/Delco pump will probably run you $90 from a dealer, you'd have to buy the strainer extra. If you have time to wait, you could always try those online parts stores like http://www.expressautoparts.com and http://www.partsamerica.com ... I always use those websites to look up part #s so the idiot behind the Pep Boys counter doesn't give me the wrong part!

POR-15 is amazing. http://www.por15.com for more info. I used their Super Starter Kit ($20) when I rebuilt my 3.73/posi/disc axle, and the kit was enough to give the axle two coats. POR-15 will harden up over time; so it doesn't make sense to buy a gallon of the stuff for $50 if you're only gonna use a little bit.

An alternative would be http://www.eastwoodco.com , type "tank zinc" (without the double quotes of course) into their little search box. You could shoot the tank with that... I'll do that when I drop the tank to install my AC pump. Eastwood also has a gas tank treatment that you could try if you feel adventurous; looks kinda nifty. Type "tank sealer" into their search box to dig up their stuff; you can buy just the sealer, or a whole kit of stuff to use.

 

Hey TomP,

I with you on GM parts but i cant afford them right now. And that Carter from Advance (partsamerica) comes with everything ( pulsator, seal, etc..) so at this time that is what i am going to buy. So back on the first topic any ideas as to why i am only getting 7 volts back to the pump? Thanks

-Buck

 

vsixtoy went with I belive an 1989 corvette fuel pump
I went with a 1991 350TPI fuel pump

Good deal on finding bad pump. When I installed my pump it came with hose clamps.

I found later the pump was not my problem and installed it(stock 1991 3.1) into my s10 when I went MPFI on it. I had to buy two small normal hose clamps and 1ft (basterds wouldnt just cut me off 2") of napa high pressure hose.

 

LOL about the 2" part... I've got a few of those from my tank-dropping jobs. (I always replaced the return hose, tank vent, and evap canister hoses.) They're handy tho for remembering what size hose ya used; usually I label them and stick 'em in a box so I can find them later.

I hear ya on the price, Buck; better to have any kind of pump than the sludge you found in the tank! But if you're still getting 7 volts at the back of the car, it's gotta be a short in circuit 120; just run a new wire from the front of the car to the back of the car and you'll be all set. You get 12 volts off the tan/white wire at the relay, at the front of the car, right?

 

Yes there is 12 volts at the tan/white wire, ECM checked out fine also. Hopefully I will have somebody to help me this weekend test that connector where the fuel pump connects, again. When the relay clicks on is that when it sends 12 volts to the pump, when you first turn the key on, or can i test it with the key on and get 12 volts all the time. If it sends 12 volts back there all the time ( remember the car has not been cranked yet ) then i should be able to test it myself. And which wire does the 12 volts come from to feed the pump, which is the fuel gauge and which is the ground? Also my fuel gauge needle is slammed up to the top, and i figured that would have been because the float was stuck, but it was not the problem, it was fine so when i take the pump out it should register EMPTY but it stays up at the top, so that very well maybe saying a short circuit or grounding problem.

-Buck

 

Hey TomP:

Gas tank, and rear end, and everyhting is back together. Now i cant try the fuel pump until i put gas in it right? What im trying to say is that you cant run a pump dry even for a second cause it will burn up. If this is not right let me know.

-Buck

 

You're right, you can't run the pump dry.

 

Okay so is there a way to prime this pump or just fill the tank with gas or maybe just 5 gallons and jump A and G on the harness and make the pump come on in short burst. Also did you prime the fuel lines, meaning you let the fuel pump push the gas in the lines and then connected them to the fuel rail lines? I think that if i prime them it will make it easier. This is just one of those common sense things, but this is my first electric fuel pump so i just want to make sure that i am not going to mess anything up.

-Buck

 

As long as you put enough gas in the tank, I think you'll be fine. I think when the pump is submerged in Gas it won't overheat.

 

Okay so what you are after is the cooling effect of the gas instead of gas running through the pump, right?

-Buck

 

 

Don't forget, since the pump is more or less submerged in the fuel, it won't take long to suck up some gas and prime itself.

 

Thanks.

-Buck

 

Just an update. The fuel pump works great. I am going to start the engine tonight after i get off of work. I have no idea how i came up with 7 volts back at the pump but it seems to be working fine. Maybe it doesnt take 12 volts, but i could be wrong. Anyway just wanted to say thank you to all who gave me advice. Thanks again.

-Buck

 

Glad to hear it all works OK!

The gas going thru the pump acts as a "lube" for the gears, that's the primary reason why you can't run the pump "dry" to test it.

 

Just wanted to give yall an update. The car is running strong and is ready for the road.

-Buck

 

TomP:

Okay when I started the car the pump came on and went off with the relay. Then the oil switch kicks in with pressure. But the pump kept running with the engine not even running, until the pressure dropped and then the fuel pump cutoff. Is this normal or is it clogged up and i should buy a new one. Thanks

-Buck