i have a problem with my car. it is a 97 trans am and it has lloyd elliot heads and joe o cam. i have 30 pound ford injectors and the 340 lph fuel pump. the fuel pump has about 6000 miles on it so i dont believe that is the problem, but the car will not want to start it just cranks and cranks. i tested the fuel pressure and it is at zero with the key in the on postion. and when i can finally get the car to start it runs like crap and is only at 20-25 psi. i thought that the fuel pressure regulator was the problem so i replaced it yesterday and the car does the same thing. someplease give me some advice on what to check next!

 

My POS of does the same thing! I'm getting 40 psi. The car starts the runs really rough and then just stalls out and will not start again

 

i have searched and some of other peoples post about this problem and still have not figured it out. i tryied a new fuel pump relay, filter, and strainer on the pump its self. still nothing. has anyone had any problems with the 340 lph pumps?

 

fuel pressure has to be within the limits of original specs (+a few pounds) or the injectors won't spray properly. The stock pump should supply the engine with all needed fuel. CHECK FUEL PRESSURE .

 

Pretty sure the walbro "340" pump refers to the part number, not the volume. I think its a 255lph pump. Did you really replace all that stuff you said you did? Check the voltage to the pump at the relay and then check your ground for the pump. Unless you've killed your pump somehow pressure shouldn't be a problem.

 

Sounds like you've done everything except replace the pump...When you say 6000 miles did you buy it used, or it worked for 6000 miles prior to this install?

--Alan

 

sounds like the fuel pump. mine did the same. my stock pump put out anywhere from 0-20 with engine off, and jumped to 30 when running. replaced with a walbro 255 and we're runnin now.

 

i thought at the time that i bought my pump that combination motorsports was offering a pump bigger than the 255 which is what i thought i bought. could be wrong did all the mods to the car then blew the tranny and was down for over a year and finally got a new tranny and now i have these problems. i bought the pump new and the car has run for the last couple of weeks but not quite right so i no its not just that i had old gas because i have gone through many tanks since i got it back on the road.

were exactly is the ground for the pump and also what should the voltage be at the relay?

 

Ground for the pump is connected to a lug near the left door nearly under the driver seat.

The easiest way to see if the fuel pump is getting voltage AND ground is at connector C405. It's located in front of the axle coming through the body behind the left rear seat. Get to it by taking the left rear wheel off. On the top cavity there is a white plug with 3 wires. The upper left and upper right wires are power and ground to the pump. It's not clear if these wires are grey and black since it's been a long time since I was under there and the manual gives the wire colors up to the connector but not from the connector to the pump.

Put a meter across both of these and cycle power off and on. See if you have power for about 2 seconds.

You could also put 12 volts on the fuel pump prime connector and then measure at C405. If you don't get anything then, it's either wiring or the relay. FYI On OBDII, fuel pump prime is run thru the relay. On OBDI, fuel pump prime bypasses the relay.

All you want to confirm is the pressure of the pump with 12 volts(and ground) applied.

If you do find you have low pressure with the proper voltage and ground at the pump, try blocking the return line to see if pressure increases. You may want to check the supply lines for restrictions or blockage. I've seen many a plastic fuel line get crimped or kinked while someone was working on or near them. If not pull the pump. While you have the pump out, check the hose connecting the pump to the fuel nipple at the top of the fuel tank unit. Be sure it doesn't have holes in it.

 

i thought i had fixed my problem. i took the assembly out of the tank and was going to but the factory fuel pump back in when i found that the rubber hose that was connected to the pump was split. so i went and got some more hose and put it on and put everything back together and the fuel pressure went to 40 after cycling the key a few times just to fill the lines since i had everything disconnected. and then it fired right up and ran like it should. it was fine for a few days until today. i tryied to start the car and it had to crank a few times to start. but was then fine. was actually tring to teach my brother to drive a stick so of course he killed it a few times like expected and it just got harder and harder to start. so i got it home and hooked the pressure tester back up and it primed to about 40 and then started right up. but then i reved the motor and fuel pressure starts to drop. with the car out of gear by just revving the engine to about 3500-4000 the pressure drops all the way down to 30psi. i hope the fuel pump is not going bad because as stated above it is not that old but what i was wondering is could the fuel pressure regulator i bought be defective. just was wondering if anybody would have any ideas as to why the fuel pressure would drop by just revving the motor.

 

Check your fuel filter and make sure the vacuum reference line is hooked up with no leaks.

 

the fuel filter is brand new and the vacuum reference line you are referring to is the on from the intake to the fpr isnt it? if so then yes it is hooked up and i didnt find any leaks. do you think it could be the fpr.