Greg1309

I've been having this issue for months. The engine will start after I hear the pump prime for 2 seconds. Many times, not always, after I run the car and shut it off it won't prime until I let it sit for awhile. The car runs great and the fuel pump has only 2000 miles on it. I switched the fuel relay with the exact one next to it but that didn't help. I am at a loss with this car not priming now and then. The SECURITY is OK the light always goes out. I just put in all new ignition parts, plugs, wires, coil, pick-up coil, ignition control module ( tried two different ones thinking that may help, it didn't) D/cap Rotor, new fuel filter. Like I said the car runs fantastic, put your foot into it and it ROARS. It's just this darm priming problem that happens when you try and re-start after the engine is hot and like I said it sometimes does prime, sometimes not.. I did a code check, EGR valve, no surprise, but nothing else. The engine light will come on ONLY with high speed driving after about 10 minutes (EGR) like I said. The light never comes on with low speed driving, off the Interstate highway driving, speeds under 50. It's a one owner car (me) and has only 32,000 miles on it.

vetteoz

iTrader: (13)

How do you know your problem is the fuel rail is not being pressurized ( what pressure does it show on gauge ? )
and that your hot start problem is not actually injector related?
As soon as you crank the engine over the fuel pump runs from the OP switch so that takes out any pump related ( prime ) start problem

Done of which are related to pump prime

Greg1309

When I try and re-start, after the engine is HOT, I can't hear the pump priming. If I let it sit awhile, an hour or so, I can hear the pump prime and it will start. The problem is that it many times it will not prime when the engine is hot. After I HEAR it prime it starts and runs EXCELLENT. I can drive it anywhere but never shut it off until I get home or I will be stuck where
ever I shut it off. I even keep it running at gas stations. Fantastic car but it is only running now to and from HOME with no turning off the key.

Greg1309

BTW, the ECM will not let the fuel pump run until it sees RPM's. I can use starting fluid but it runs a second or two and stops. The fuel relay is working but the pump won't start up all of the time and prime the system like it's suppose to before the ECM let's it run full time. When the pump does prime the engine starts and runs FANTASTIC.

Damon

I am not sure if the pump does prime every single time. Thee may be some conditional logic in the ECM related to temp or who knows what.

The main thing is that once you hit the starter the fuel pump should be running, regardless of whether it did the 2 second prime cycle or not. It's just looking for an RPM reference signal from the distributor.

I agree that your no-prime and no-start conditions are related, but maybe not for the reason you think. Flaky ECM or something you haven't considered.

FYI- there are two parallel paths for voltage to reach the fuel pump. One is the ECM activating the ful pump relay (the primary path everyone knows about) and a backup path through the Oil Pressure Sending Unit that is screwed into the block just above the oil filter. That second one will supply voltage directly from the battery to the fuel pump any time you have more than ~6 PSI of oil pressure. Many engines can muster about that much pressure just flipping over on the starter, but not all of them.

Not sure if I'm helping you here, but I thought you might like to know a little about the electrical system and how it supplies the fuel pump with voltage.

vetteoz

iTrader: (13)

Ecm runs pump ( through relay ) for 2 sec when you turn the key on to prime the rails then it stops.
Ecm does not run pump again until the ECM see the ref pulses from the dist showing that the engine is turning over.

The OP switch however runs pump direct as soon as you have more than 4 psi oil pressure so pump ( if working ) should run as soon as you crank the engine over , giving you fuel pressure and engine should fire up

Maybe the fault is with the pump itself and it won't work when hot?

When it won't work put 12V to terminal G of the ALDL connector.
That will supply power direct to pump , bypassing the OP switch and pump relay to prove if pump actually works as it should when hot

Greg1309

The pump has 2000 miles on it and the engine runs fantastic when started. I can drive it all over town and to Daytona and back, no issues. It just won't PRIME about half the time when you shut the engine off and try and restart. I did have an issue with the speedometer last week. It quit running and would bounce around now and then. I changed the VSS and it still didn't work. I drove it around town and it would not work most of the time just bounce around. I was going to change the VSS Buffer but, just for fun, I disconnected the battery for a few minutes, hooked it back up and then drove the car. The speedometer works great now, after disconnecting the battery and reconnecting, no problems. I have no idea why that worked but I ain't complaining. Maybe I have a ECM problem not sending the fuel relay a good signal all of the time. Maybe I should get out my hammer.

vetteoz

iTrader: (13)

And you are still MISSING THE POINT.
The pump does not need to prime in order for the engine to start and continue running;
as soon as you crank the engine over , the OP switch will make the pump run ( assuming your OP switch actually works? )
Will take slightly longer crank time but engine will still fire up
You could remove the ECM controlled relay altogether and engine would still start

vetteoz

iTrader: (13)

Greg1309

Yes, you are correct TWO paths for volts going to fuel pump BUT, the ECM has to see RMP's for the pump to keep running. Without the relay sending a signal to the pump to PRIME it will not start. That is a saffety factor in case you have a wreck, the ECM turns the pump off when there are no RPM's showing. That is the way it works on this model others may be different. This model needs RPM's being seen by the ECM to keep the pump running even if it had a dozen wires with 12 volts running to the pump.

vetteoz

iTrader: (13)

Might like to a search on that popular myth

Your understanding of auto electrics is severely lacking.
You only need one wire with 12V on it going to the pump for it to keep running ; regardless of what any other wire ( from the ECM ) is doing
Look at the pump circuit diagram
If OP switch is closed ( from oil pressure ) ,the pump gets power direct from the batt
and continues to run even if you took the ECM and relay out of the car altogether

Aaron_SK

iTrader: (1)

vetteoz is 100% correct. The point of the oil pressure switch was to keep the car running in case of relay failure.

I have seen cars that had a bad fuel pump relay. They would never prime and had to be cranked for a bit before they would start.

I suspect you have a hot-start issue that is unrelated to the pump priming. Even if your relay were to heat soak and fail at a gas station, if you cranked the car for long enough it would fire off the oil pressure switch. If this is not happening then I would venture a guess that your problem lies elsewhere.

TwinTurboROC

I see you trying vett but dam your hurting to get the point across.

Ok re-stating what vettoz said:

Any camaro or firebird, will start up, even if it has NOT PRIMED. IT WILL TAKE 3-5 seconds longer to start up.

Pumps prime to pressurize the fuel rails so you dont have to crank your car for so long.

As long as your Fuel Pump relay OR your Oil pressure switch is ok, your car should start up.

Now assuming that you have a heat soak issue, and lets just assume your oil pressure switch is bad. You are left with 3 possible problems, A bad pump (even though its new), a bad relay, or a bad ecm. Now since your ecm is no where near heat (it may still overheat internally) we can leave that on the back burner. Switching 2 old 20+ year old relays really isnt the safest way to be assured its not the relay.

If you have TBI car you will be checking the Tan/white wire instead of the grey wire

This is for the TPI's
My suggestion, take a test light or a multi meter, and probe the grey wire coming out of the fuel pump relay when your having this problem. That is the power feed + to the fuel pump. You can check to see if it has voltage or lights up when you turn the key to ignition on or run. It will only give you a brief power signal. If you want to test it again you will have to turn the car off and wait about 10-15 seconds. The ECM will not prime the car again if you try it quicker. IF you see that wire giving power aka test light lighting or 12+ volts on the multimeter, your fuel pump or someting related in that area is bad.

IF you have power coming from the feed line. I would suggest testing the same color wire at the back of the car where the fuel pump harness connects to the cars harness. (right above the trans tunnel, on the back wheel hump) Also I would check to make sure there is adequate ground.
If all is ok, then the pump is bad. Replace it.

IF you have no power coming from that power feed, then you can check the ecm signal to prime the pump. That is the dark green/white wire on the relay. It will only come on for about 2 seconds, then you will have to turn the ignition off, wait 10-15 seconds again, then try to prime it again.

If you see a signal there, but no power feed to the pump, your relay may be getting stuck. Replace it.

If there is no signal on the dark green/ white wire, you may have a boned PCM.


I tried to make this as simple as possible. Get back to us with results. AND LISTEN TO VETTOZ!!!!!!!!!

TwinTurboROC

BTW my guess is a crapped out pump.

Greg1309

Updating------Went to start the car up the other day after it sat for a few days, in other words a cold engine start. No sound of pump priming, engine would crank but not start. Now the won't start hot theroy is out the window. Just for the heck of it, don't ask me why, I got out of the car went back to the side where the fuel intake is (fuel cap) and shook the car back and forth from side to side a few times. I got back in the car and it fired right up. Went for a long drive, stop and go, highway speeds, the car runs like new, idles like a purring kitten, stomp on the gas and it roars like a lion. So what is going on. Is moving the tank assembly around like smacking an old tube type tv to get it to act right. The pump has 2,000 miles on it, could this have something to do with the sending unit getting hung up now and then? I sure hate to spend a lot of $$$$ to replace a fuel pump with 2,000 miles on it. Is the crap gas with the corn in it the blame? I use premium name brand fuel but it still has the corn in it. I also use Lucas fuel treatment in all of my cars and motorcycle, I buy the stuff by the gallon.

TwinTurboROC

Well it could be a bad connection, but i doubt that. Usually when fuel pumps are going bad, and someone is stuck, you can hit the tank a few times with a rubber hammer, or in our case hit the back hump. This will giggle the armature windings of the fuel pump loose. Enough for it to start up and keep running.

There's a few different way fuel pumps die, some have electrical failure on the windings, others have overheat issues where thee (for lack of a better description) melt basicly. What happens is that it shifts internally and causes a jam on the rotor vanes.

Is the pump still under waranty?

On a side note, did you check the fuel pump connector/harness near the back of the car, Going from the body to the tank. Make sure its seated properly.

GL

Greg1309

Connector was taken off, voltage to pump detected and connector replaced to a snug fit. I think you may be right about getting the pump to work by giving it a shake. I had a mechanic tell me that the ethanol fuel is destroying the impellers on the fuel pumps. Another government program that is hurting consumers and destroying their cars to make corn farmers richer. I'm too old, have a very bad back and no lift so I guess this is going to cost me $$$$$$$$$$$. Well, I still have a beautiful 91 Camaro with only 32,000 miles on it and no car payments. Count my blessings.

TwinTurboROC

That is true. FP jobs usualy run around 350 bucks with the pump inlcuded. Extras are usually a fuel filter (most shops wont do the warranty w/o doing this) and some places boil the tank out.

Greg1309

The last time I had it done was in New Smyrna Beach, Fl and it cost me about $525.00, it lasted 2000 miles, OUCH!!!

kevinlcook95

Greg did you ever get the problem solved? i am having the same EXACT issue with my 89 gta 5.7. i have replaced all the same exact stuff too except EGR valve and im getting the same results as you are>

Greg1309

I'll know when I get this fuel pump changed. I do have a 1963 Ford Falcon Convertible I can always rely on. The fuel pump for it runs about $30.00 and takes about 15 minutes to change. I keep a set of points and condenser in the glove box for any ignition problem. The old cars are much more owner friendly. A plus is that I get a lot of people waving at me when driving.

Greg1309

Update: I had a new fuel pump installed and now everthing is fine, once again life is sweet. BTW, I looked up the part # on the old receipt that I got when the last one I had installed by a garage in New Smyrna Beach. To my shock they installed a POS pump that they bought at Advance Auto Parts, an Airtex brand made in China that has HORRIBLE reviews. I got 2000 miles out of it. This time I took my own pump and screen in when I went to get it replaced, I bought a BOSCH at Advanced for a few $$$$ more and now have something decent in the tank. I had no idea a shop in business to repair cars would use such junk, IDIOTS. Lesson learned, if someone else is working on you car DEMAND quality parts be installed, pay a little more get less grief. I ASSUMED these people that put in the last pump would do right by me, MY MISTAKE, MY $$$$ flushed.

Iroccer

iTrader: (1)

I'm having fuel pump problems so I got a new one an airtex. Put in did not work so I got another this time I tested it on the bench didn't work. So I got on here and ran across the this thread. conclusion airtex is junk. I'm going to buy a walbro or bosch

Greg1309

Lesson learned just like me. Read the reviews on the parts BEFORE buying. I had a hard time wrapping my head around the pump not lasting but 2000 miles UNTIL I read the reviews. This is why I looked for EVERYTHING else besides listening to people who kept telling me I had a fuel pump problem. It's a pleasure driving my beautiful Camaro now without the mental anguish of trying to figure out why it would not start from time to time.

stue

Ive been having a similar problem with my 91 3.1 changed everything but seems to be the cable going in to the ecu plug was loose for instance with vibration or somebody slamming the passenger door pump would not prime,jiggle the wire in the plug and it will prime,still looking for a schematic diagram for the ecu,not a wiring diagram but one for the internals of the ecu

D&S 85 IROC

how about this one my fuel pump doesn't prime at all. Turn the key on fuel pump run continuous,

Biggd4355

I am having similar problems with both my 1989 Camaro and my 1993 chevy truck. For some reason, the fuel pump isn't being activated. So I have ran a switched wire to the grey wire going to the fuel pump. If I turn the power on, they start right up and run beautifully. I have replaced the oil pressure sending units. That isn't the problem. Whatever the problem is, they both share it.

altownsend

1986 Fiero V6 4-Speed

Fuel pump will not prime

I have a good 12 volt constant at key 'On' position at the green/white prime wire coming from the PCM

When I bridge/jump the prime wire (green/white) to the fuel pump wire, key 'On', I do not get a prime. But, I can put 12 volts to the fuel pump wire and get the pump to power on. It will not prime when I jump the green/white to the fuel pump lead with key 'On". I can read 12 volts constant between green/white and fuel pump wire.

Anyone have a fix?

GeneralDisorder

iTrader: (1)

First off this is a thread from 2012.

Second - this is a third gen Camaro and Firebird forum so most of us would have no idea about the wiring on a Fiero. Those wire colors are meaningless to us.

I suggest you get a factory service manual on ebay, and find a forum dedicated to Fiero's.

GD