Been chasing this problem" literally for YEARS". 85 4 cyl / auto . car would Always start and run good, Great low miles car, but every once in awhile just DIE, wait 30 seconds and it would start again. About 6 months ago I installed a" Mechanical fuel Pressure gauge" in the console (so I could "Watch" the fuel pressure when the problem presented itself). car would start and run fine as usual,(also ran a wire with a button from the lighter to the fuel pump). haven't messed with it for a long time now, almost a year. But always went out and ran it for awhile. today, I went out and it started right up, ran for about 2 min and quit. But "This time" I was able to "watch the fuel Pressure As it died" !!! as it was dieing, I jumped the hot wire from the lighter to the pump and the pressure would NOT COME UP ! Waited about 5 seconds and tried it again and the pressure went right up and started and ran fine, then pressure dropped and it shut down. SO SOMETHING IS GOING ON WITH THIS FUEL PUMP, when it works the car starts and runs fine, but sometimes EVEN HOT WIRED, it will not build fuel pressure ! (Pump will Not run even Hot Wired). 5 seconds later it will. So even with Pump being" hot wired", it won't start, gotta be the PUMP ! all lines are clean, new filter, new injector. yes there's gas in it. if the pump will not run "hot wired", got to be the pump overheating or something. Gotta love all this Chinese made garbage.
Do you still have the original sending unit in it. If so that could be shorting out that happened on my current 86 gt I just bought back in June of last year. Car would run fine for 5 minutes but then die out thinking it was the pump get a new one install it car starts then just stall. I found out the wire on the connector going into the tank so so corroded that it was causing a open circuit not sending power to pump. Replaced the sender and all is good now been driving it daily since 😊. I will suggest if you get one from the fiero store that you remove that crappy black float that comes on it transfer the orange float from the original. You can also cut a inch off it and the lever so it doesn’t hit on the baffle inside the tank. My sender is dead accurate as well now 190 miles to a full tank 2.8 4 speed keeping it at 65.
Originally posted by Phil: Sounds like a fuel pressure regulator problem
Has not electrical parts and won't cause FP not running.
Originally posted by pontiacfierokid1985: Do you still have the original sending unit in it. If so that could be shorting out that happened on my current 86 gt I just bought back in June of last year. Car would run fine for 5 minutes but then die out thinking it was the pump get a new one install it car starts then just stall. I found out the wire on the connector going into the tank so so corroded that it was causing a open circuit not sending power to pump. Replaced the sender and all is good now been driving it daily since 😊. I will suggest if you get one from the fiero store that you remove that crappy black float that comes on it transfer the orange float from the original. You can also cut a inch off it and the lever so it doesn’t hit on the baffle inside the tank. My sender is dead accurate as well now 190 miles to a full tank 2.8 4 speed keeping it at 65.
Crap Level Sender shouldn't cause no power to pump.
+ wire from gauge to sender. + wire from Relay, OPS and and ALDL G to pump. Ground wire for both goes into cabin to ground @ G201 & G202.
Can easily back probe all of them at C502 under Wire Bulkhead pass-thru in engine bay. Can disconnect to try to check wires from there to the tank w/o dropping the tank. Can check ground on car side too.
Tank and sender/pump plumbing is a crap ground at best w/o the ground wire being good. This might get connection to run the pump but never made to do so.
Shorted sender Should = Gauge reads Empty all of the time. But Iffy Ground wire can "kill power" to FP & Sender and might fry either or both.
------------------ 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)
bad "wire" about 4" Before the" 203" plug, coming From the car to the 203, not going out of the 203. wasn't the connection, was actually a Bad Wire "INTERNALLY" . if I "bent" the (TAN/White)wire the pump would stop ! I "rewired" from 1 foot Before the 203 to 6" After the 203, ( bypassing the 203 plug altogether). now it seems to be fine. Never would have suspected a wire going bad "internally" with NO "External" damage ! I took it for a couple mile ride, seems fine now. find out for sure tomorrow. If i didn't have that mechanical FP pressure gauge to "watch", I probably never would have found it . LOL
Originally posted by Lou6t4gto: Never would have suspected a wire going bad "internally" with NO "External" damage !
Oh yes... Wires Can rot or break w/o obvious damage to the insulation. Seen this on cars and more.
2 quick examples: WeatherPac and others types Are Not water proof only weather resistance and drive thru deep water etc then polluted water on wires can get into most connectors. More so when wires are loaded so seals won't seal right or no at all.
Insulation pierced to test then some fool didn't do anything to seal the hole.
THERE IS NO END TO THIS !!!!! went out today to move it , turned the "key on", and "NO Pump Pumping" !!!! really starting to piss me off. I have a brand new pump that I'm going to install, this time it is going to get a wired Directly from the fuse box to the pump ! I've already tried everything "Reasonable", Now it WILL RUN !!!. is there any reasonable REASON ,"NOT to do it this way ???? Isn't there a thread on direct wiring the fuel pump somewhere on here ?? Thanks
wired from the lighter to the Fuel pump at the test point under the console, at first nothing, no pumping at all (only a spark at the connection, so it was sending power to it), tried the key again and it cranked and started, ran about 2 seconds and pressure dropped went down to 3 pounds and quit. hot wired from lighter to fuel pump. went up to 13 psi,then ran, and dropped to 0 again, would not bring fuel pressure up again. ordered new oil pressure sender, doubt it will make a difference, I have a new pump so I will install it and replace EVERY wire and Connection from the sender in the tank to the plug on the rear firewall.
hot wired from lighter to fuel pump. went up to 13 psi,then ran, and dropped to 0 again, would not bring fuel pressure up again.
When that occurs, can you still hear the fuel pump running? If yes, then possibly there's an issue with that short length of hose inside the gas tank. If no, I suspect the fuel pump itself is faulty... or, as you're already suspecting, a fault with the wiring (even though using the ALDL terminal eliminates a lot of the wiring).
[This message has been edited by Patrick (edited 03-19-2020).]
just bought and installed a NEW FUEL PUMP yesterday. Before re installing the tank, (with pump installed) I used jumper cables and checked that the pump did indeed" RUN" before I put the Tank back in the car. The pump "ran", but pumped NOTHING! checked all the hoses to make sure there was nothing plugged or leaking. all fine. then I thought "do I TRUST" that this thing was MADE Correctly ! the pump would run but pumped Nothing, because the pump was running BACKWARDS ! The new plug (pigtail) that came with the pump was wired Backwards (color coded)(neg in positive place and positive in neg spot !!!!!) changed it around and now it works fine. ****So Far !**** ;-) -- WHY can't we buy parts that "actually Work Correctly" right out of the package anymore ???! Doesn't seem to matter what brand.
Was the old pump dead? was when I took it out, Now jumping it "out of the tank", it spins ! "IN" the car, it WAS getting power sent to it, but would not run. yes, when the tank was out, I Checked EVERY WIRE AND CONNECTION from the pump to the sender, the sender to the plug, plug to 203, 203 to fuse, there was power at the relay and the relay is new.
I had a problem with an S10 where the fuel pump would randomly not work. Turned out to be a loose terminal in the plug that plugged into the fuel pump. Dropped the tank several times before finding it. Solved it by testing the pump out of the tank and wiggling the wires. You don't want to be pumping gasoline when testing the pump outside the tank. I used diesel. But the problem came down to a terminal that had gotten too loose on the pin inside the connector.
The final solution was to solder the terminals directly on the pump's pins. It solved the problem.