ok I installed my new walbro 255 lph fuel pump last weekend, and now I've got problems. before the pump install my old pump was whining but the car ran ok. now the car has a surging idle it idles up and then down, up, down. and when i try to drive it it starts to cut out like it's not getting enough fuel. what do you think my problem could be? i looked at the lines but they don't look pinched or anything. I'm gonna yank the tank again tomorrow to see if i can figure out what's wrong with it.
new fuel pump and now I have new problems.
- Thread starter goldbomb79
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you don't have an adj. fuel pressure regulator listed in your sig. if you don't have one then I would suggest getting one since you stepped up to a larger sized pump.
Here's a great check list that someone from Stangnet put together for determining whether you have a spark or fuel problem. The list has been showing up quite often these days 
First find out what system is failing: Is it fuel or ignition? Here's a checklist to help eliminate the things that aren't the problem.
Cranks OK, but No Start Checklist for Fuel Injected Mustangs
1.) Remove push on connector from starter solenoid and turn ignition switch on. Place car in neutral or Park. Remove coil wire from distributor & and hold 3/8” away from engine block. Jumper the screw to the big bolt on the starter solenoid that has the battery wire connected to it. You should get a nice fat blue spark.
Most of the items are electrical in nature, so a test light, or even better, a voltmeter, is helpful to be sure they have power to them.
No spark, possible failed items in order of their probability:
A.) Coil
B.) TFI module
C.) PIP sensor in distributor
D.) ECC relay next to computer
E.) Fuse links in wiring harness
F.) Ignition switch
G.) Computer
2.) Spark at coil wire, pull #1 plug wire off at the spark plug and check to see spark. No spark, possible failed items in order of their probability:
A.) Moisture inside distributor – remove cap, dry off & spray with WD40
B.) Distributor cap
C.) Rotor
D.) Spark Plug wires
E.) Coil weak or intermittent - you should see 3/8" fat blue spark with a good coil
Spark at spark plug, but no start.
Next, get a can of starting fluid (ether) from your local auto parts store: costs a $1.30 or so. Then pull the air duct off at the throttle body elbow, open the throttle, and spray the ether in it. Reconnect the air duct and try to start the car. Do not try to start the car without reconnecting the air duct.
Two reasons:
1.) If it backfires, the chance for a serious fire is increased.
2.) The computer needs to measure the MAF flow once the engine starts.
If it starts then, you have a fuel management issue. Continue the checklist with emphasis of fuel related items that follow. If it doesn’t ,then it is a computer or timing issue: see Step 4.
Clue – listen for the fuel pump to prime when you first turn the ignition switch on. It should run for 5-20 seconds and shut off. To trick the fuel pump into running, find the ECC test connector and jump the connector in the lower RH corner to ground. See http://www.mustangworks.com/article...c-iv_codes.html for a description of the test connector. If the relay & inertia switch are OK, you will have power to the pump. Check fuel pressure – remove the cap from the schrader valve behind the alternator and depress the core. Fuel should squirt out. Beware of fire hazard when you do this.
No fuel pressure, possible failed items in order of their probability:
A.) Tripped inertia switch – Coupe - press reset button on the inertia switch located by driver’s side rear shock absorber. Most of the time, you can remove the plastic access cover over the shock absorber top mount to get at it. The hatch cars hide it under the plastic trim covering the driver's side taillight. Use the voltmeter or test light to make sure you have power to both sides of the switch
B.) Fuel pump power relay – located under the driver’s seat in most stangs built before 93. On 93 and later model cars it is located below the Mass Air Flow meter.
C.) Clogged fuel filter
D.) Failed fuel pump
E.) Blown fuse link in wiring harness.
F.) Fuel pressure regulator failed. Remove vacuum line from regulator and inspect for fuel escaping while pump is running.
4.) Spark & fuel OK.
A.) Failed IAB (no airflow to start engine). Press the throttle ¼ way down and try to start the car.
B.) Failed computer (not very likely)
C.) Engine ignition or cam timing off only likely if the engine has been worked on recently).
Work through the chcklist until you find the suspect area, then repost if you need more help
First find out what system is failing: Is it fuel or ignition? Here's a checklist to help eliminate the things that aren't the problem.
Cranks OK, but No Start Checklist for Fuel Injected Mustangs
1.) Remove push on connector from starter solenoid and turn ignition switch on. Place car in neutral or Park. Remove coil wire from distributor & and hold 3/8” away from engine block. Jumper the screw to the big bolt on the starter solenoid that has the battery wire connected to it. You should get a nice fat blue spark.
Most of the items are electrical in nature, so a test light, or even better, a voltmeter, is helpful to be sure they have power to them.
No spark, possible failed items in order of their probability:
A.) Coil
B.) TFI module
C.) PIP sensor in distributor
D.) ECC relay next to computer
E.) Fuse links in wiring harness
F.) Ignition switch
G.) Computer
2.) Spark at coil wire, pull #1 plug wire off at the spark plug and check to see spark. No spark, possible failed items in order of their probability:
A.) Moisture inside distributor – remove cap, dry off & spray with WD40
B.) Distributor cap
C.) Rotor
D.) Spark Plug wires
E.) Coil weak or intermittent - you should see 3/8" fat blue spark with a good coil
Spark at spark plug, but no start.
Next, get a can of starting fluid (ether) from your local auto parts store: costs a $1.30 or so. Then pull the air duct off at the throttle body elbow, open the throttle, and spray the ether in it. Reconnect the air duct and try to start the car. Do not try to start the car without reconnecting the air duct.
Two reasons:
1.) If it backfires, the chance for a serious fire is increased.
2.) The computer needs to measure the MAF flow once the engine starts.
If it starts then, you have a fuel management issue. Continue the checklist with emphasis of fuel related items that follow. If it doesn’t ,then it is a computer or timing issue: see Step 4.
Clue – listen for the fuel pump to prime when you first turn the ignition switch on. It should run for 5-20 seconds and shut off. To trick the fuel pump into running, find the ECC test connector and jump the connector in the lower RH corner to ground. See http://www.mustangworks.com/article...c-iv_codes.html for a description of the test connector. If the relay & inertia switch are OK, you will have power to the pump. Check fuel pressure – remove the cap from the schrader valve behind the alternator and depress the core. Fuel should squirt out. Beware of fire hazard when you do this.
No fuel pressure, possible failed items in order of their probability:
A.) Tripped inertia switch – Coupe - press reset button on the inertia switch located by driver’s side rear shock absorber. Most of the time, you can remove the plastic access cover over the shock absorber top mount to get at it. The hatch cars hide it under the plastic trim covering the driver's side taillight. Use the voltmeter or test light to make sure you have power to both sides of the switch
B.) Fuel pump power relay – located under the driver’s seat in most stangs built before 93. On 93 and later model cars it is located below the Mass Air Flow meter.
C.) Clogged fuel filter
D.) Failed fuel pump
E.) Blown fuse link in wiring harness.
F.) Fuel pressure regulator failed. Remove vacuum line from regulator and inspect for fuel escaping while pump is running.
4.) Spark & fuel OK.
A.) Failed IAB (no airflow to start engine). Press the throttle ¼ way down and try to start the car.
B.) Failed computer (not very likely)
C.) Engine ignition or cam timing off only likely if the engine has been worked on recently).
Work through the chcklist until you find the suspect area, then repost if you need more help
ok, as i said before the car ran ok before the new fuel pump, it's just the pump was starting to whine something fierce so I decided to upgrade to a new pump. I had a afpr but i sold it like an idiot from my last project. shouldn't the fuel pressure be the same with the new pump since I was using the stock regulator before and it was fine. and now with the new pump it's doing this crap. I guess i'd better just pull the tank again and see what is wrong. could i possibly have a leak somewhere or caused one?
Do yourself a favor and check for fuel pressure at the schrader valve before dropping the tank. Maybe it's a clogged filter, maybe you damaged one of the fuel pump wires reinstalling the tank? Could be a bad ground wire? Who knows? But why go through the trouble of dropping the tank when you don't even know what is causing the problem fuel or spark. Go through the check list and narrow down the problem.
ok it's not spark when i had spark like a few hours before I started the car up with the old pump. i got under the car with it running and i can here the pump running so it's not cutting out. also, the fuel pressure should be the same seeing how i didn't mess with the regulator or injectors just the pump was changed. and i did install a new filter so it's not clogged either. any other people have any ideas
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