fuel pump prime / cold start
10-10-2017, 07:57 PM
#1
fuel pump prime / cold start On my 1997 Formula, the fuel pump prime seems to be high pitched for a split second before it sounds normal. I then have to hold the key in the start position for a full second before it fires up (used to be a half second cranking). Any ideas before I start guessing again? Already had the fuel pump replaced 5 years ago....could it be the fuel pressure regulator? I guess I should probably hook a fuel pressure gauge to it (or worst case, take it to a shop only to be told nothing is wrong even though I am sure something is wrong as it has not done this before). Thanks!
Car has 38000 miles, and other than the weird initial pump noise, the car runs awesome...
Car has 38000 miles, and other than the weird initial pump noise, the car runs awesome...
10-10-2017, 08:09 PM
#2
TECH Enthusiast
put a gauge on the schrader valve on the back of the intake. cycle the key on and off and watch the gauge. basically if you can watch the needle drop rather fast, then the regulator is bad. this would cause the prolonged start
10-10-2017, 08:47 PM
#4
11 Second Club
iTrader: (3)
Isn't the fuel pressure regulator on the fuel pump assembly.
10-10-2017, 09:27 PM
#5
Get a fuel pressure gauge. They are around $50. It just screws on to the Schrader valve on the back of your fuel rail. Right next to the Fuel pressure regulator. Fuel pressure should immediately snap to around 38 PSI when you turn on the key. If it bleeds off after you shut key off no big deal. As long as it holds fuel pressure when engine is running and does not drop while accelerating.
after you shut off engine pull the small rubber elbow off the fuel pressure regulator and check to see if there is any signs of fuel in it. If so FPR is bad.
OP has a LT1 car. FPR is on fuel rail, rear.
10-12-2017, 08:44 PM
#6
I know it's rough to diagnose over the internet. I tried to give as much detail as possible to see if anyone has encountered this before.
Today I tried priming 3 times before starting. Only the first prime sounded abnormal with the high pitch. 2nd and 3rd primesbsounded normal but the cold start still took a good second of cranking before it fires up. Once running, no sputtering or anything, car runs smooth at idle and strong when moderate to WOT, never runs rough or stalls.
I was thinking maybe there is a leak somewhere but I don't smell any gas in my garage where my car stays when not in use.
I may just take it to the dealer and see if they can thoroughly check the fuel system (maybe there is a leak I am unaware of).
Today I tried priming 3 times before starting. Only the first prime sounded abnormal with the high pitch. 2nd and 3rd primesbsounded normal but the cold start still took a good second of cranking before it fires up. Once running, no sputtering or anything, car runs smooth at idle and strong when moderate to WOT, never runs rough or stalls.
I was thinking maybe there is a leak somewhere but I don't smell any gas in my garage where my car stays when not in use.
I may just take it to the dealer and see if they can thoroughly check the fuel system (maybe there is a leak I am unaware of).
10-18-2017, 07:40 PM
#7
Took it to the dealer, they couldn't replicate on a warm engine.
They kept it overnight so they can replicate a "first thing in the morning" cold start.....and they say it's the fuel pump.
What causes these pumps to prematurely go bad?
They kept it overnight so they can replicate a "first thing in the morning" cold start.....and they say it's the fuel pump.
What causes these pumps to prematurely go bad?
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10-18-2017, 08:57 PM
#8
TECH Enthusiast
saw your post about the dealership. be cautious because they might just say its the pump not really knowing how to trouble shoot these motors. they most likely will hit you with a huge quote for replacing the pump
10-23-2017, 02:21 PM
#14
If you are not doing this work yourself you don't really know WTF a service shop did. Yeah they put in a "new" pump and sent the car on its way if it started.
You may have a "intermittent" wiring issue to the pump that now may be permanent which is easier to track
A DVM would help in tracing voltage to pump to confirm it is getting power.
Confirm FP relay is good and check to see if any signs of the pins of the relay are not burnt
you say it "failed" while driving. I assume you checked fuel pressure to determine this, right?
You may have a "intermittent" wiring issue to the pump that now may be permanent which is easier to track
A DVM would help in tracing voltage to pump to confirm it is getting power.
Confirm FP relay is good and check to see if any signs of the pins of the relay are not burnt
you say it "failed" while driving. I assume you checked fuel pressure to determine this, right?
10-24-2017, 11:44 PM
#15
Unfortunately I don't have details as to why the new pump failed. It happened when the dealer was road testing the car after installation so I have to wait for them to investigate and provide better details.
One possible cause they told me is because I am not driving it enough. They questioned the gas I've been using (BP Ultimate 93....every time).
One possible cause they told me is because I am not driving it enough. They questioned the gas I've been using (BP Ultimate 93....every time).
10-25-2017, 10:50 AM
#16
TECH Fanatic
Are you the original owner? Any idea what kind of shape your gas tank is in?
My car sat in a garage for several years with no prep and wasn't driven. When I pulled it out of storage, I had to replace, among many other things, the fuel pump. I just bought a replacement at an autoparts store and I'm sure it wasn't an OEM pump. It failed prematurely. I attributed that failure to my gas tank being full of rust, which I learned after the fact upon closer inspection. Whether or not that was actually the cause, I have no idea. It may have just been a bad pump. I replaced the failed pump with an AC/Delco, and also replaced the gas tank at the same time. Many years later my car still isn't being driven, but the AC/Delco pump is still working.
My car sat in a garage for several years with no prep and wasn't driven. When I pulled it out of storage, I had to replace, among many other things, the fuel pump. I just bought a replacement at an autoparts store and I'm sure it wasn't an OEM pump. It failed prematurely. I attributed that failure to my gas tank being full of rust, which I learned after the fact upon closer inspection. Whether or not that was actually the cause, I have no idea. It may have just been a bad pump. I replaced the failed pump with an AC/Delco, and also replaced the gas tank at the same time. Many years later my car still isn't being driven, but the AC/Delco pump is still working.
10-31-2017, 06:12 PM
#18
Car is back.....better than ever!!!!!
But -- with the new fuel pump and level sending unit (all built into one unit), cones an inaccurate fuel gauge. When the tank is full, the gauge is between 3/4 and F. Same thing with the last replacement fuel pump.
Also, is it normal to smell gas from the rear after it was just running?
But -- with the new fuel pump and level sending unit (all built into one unit), cones an inaccurate fuel gauge. When the tank is full, the gauge is between 3/4 and F. Same thing with the last replacement fuel pump.
Also, is it normal to smell gas from the rear after it was just running?
11-01-2017, 02:19 PM
#19
most "shops" just slap parts in as fast as they can. Time=$....although they will bill for book rate but try and do the job as fast as possible,
The "float" lever may need to be bent some to correspond with your gauge.
The "float" lever may need to be bent some to correspond with your gauge.
11-01-2017, 06:18 PM
#20
What about moving the needle on the actual gauge?
Last edited by Jeff 97 Formula; 11-01-2017 at 06:28 PM.