Like the topic says, I replaced my stock delco in-tank pump in my 1987 Formula 350 (TPI) with a Walbro 255lph pump. The install went very smoothly (once I actually got to the pump).

When I first turn the key over I can hear the pump prime and send fuel to the engine. Then when I engage the starter it turns the motor over and won't start. After trying several times the engine will start up and run perfectly. Sometimes I have to try like 8 or 9 times before it will start. Also the problem seems to get worse the longer I let the car sit after I shut it off. I've driven the car about 35 miles with the new pump and it runs great AFTER I get it started.

Before I replaced my dying stock pump it would start up so quickly I could hardly hear the starter. Now it sounds like it has problems.

Anyone know whats going on? Any suggestions?

--Dan

 

I would put a fuel pressure gauge on the rail, and see what is going on. See if it holds pressure after you prime it or leaks down. Also, check the pressure running at idle (both with the vacuum line to the regulator connected and disconnected). You might have a leaking injector or regulator if it's a fuel related problem.

 

Thanks, I try those things....anyone else?


Thanks for a fast reply. --Dan

 

TTT

 

Step away from the keyboard, go get a fuel pressure gauge, and report back with your findings as the other guy indicated.

 

I actually used my Keyboard and ordered a fuel pressure guage from Summit--should have some results in a few days. I really hope this is an easy fix, but I have a bad feeling. As many of you know the fuel pump isn't a "walk in the park" to get to---and I just swaped out last weekend!

 

Did you do the fuel filter as well as the pump?

 

Mike,

I'm in the process of replacing it now, but I'm not so sure it's the problem. ---I'll know more when the filter is replaced and my fuel guage shows me whats happing at the fuel rails.

Thanks for the advice. --dan

 

FWIW, you can get a pressure gauge at any local auto parts store or tool vendor (Mac, Matco, Strap On) that will screw into the schrader valve on the fuel rail and tell you everything you need to know.

 

Oops....never mind.

 

Did you replace the pulsator with a peice of high-pressure fuel injection hose, and 2 tight clamps?

-- Joe

 

UPDATE

OK... HERE ARE THE FUEL GUAGE PRESSURE RESULTS:


When I turn the Key to activate the fuel pump I can hear the fuel pump trying to prime the injectors.--But my fuel guage hardly moves. It may read like 2psi.

When I turn the car over and get it started up I get 35psi at the guage at idle.

When I remove the vacuum line from regulator the guage jumps to 45 psi.

When I replace the vauccum line back on the regulator it quicky jumps back down to 35psi.

When I rev the engine quickly the fuel pressure jumps up to 40-45psi depending on how much throttle I give it and how quickly I move the throttle.

What does all this mean for my particular problem?

Also:

Keep in mind I have a 255lph pump with a stock regulator and a completly stock engine with very low miles. I went with a 255lph pump becasue I plan on future mods including a Nitrous System.

The car has a brand new fuel filter.

I did leave the pulsator on with the new pump because I didn't hear differently until after the install was complete.

Thanks for your help guys!

--Dan

 

When you key it up and the pump primes, it should be 45 psi on the gauge, and stay there. You may have to key it up, wait 10 or 15 seconds, and key it up again to build the pressure, but no more. If it doesn't hold pressure, it's a bad regulator or leaking injector. I would key it twice to prime, and see what it does. If no pressure, try restricting the return line with a pair of vice grips over the rubber part (carefully, don't cut a hole in the line). If it holds pressure, leaking regulator. If not, probably leaking injector.

 

Lo-Tec,

Thanks for the very good information.

Anyone agree with this or disagree (respectfully)???


Since the car ran great before I swapped pumps, I think it would be strange to suddenly have a bad regulator or injector. On the other end of things, maybe the very powerful pump has caused an old part to fail. (?)

Anymore input is greatly appreciated.--Thanks.

--Dan

 

Let's take a step back real quick. If it ran great before, why did you swap the pump?

 

The pump was on it's last leg. It ran ok, but on two ocations it had made strange high pitch noises and my car actually died while I was driving it. So I never really knew how long I had before the pump would die for good. ---BUT BEFORE THE SWAP IT ALWAYS STARTED RIGHT UP.

With all of the mods I plan to do I thought this is would be a great time to swap out the stocker pump for a nice Walbro 255lph.

PS. Where do you recommend clamping the return line?


-Dan

 

The rubber return hose coming off of the intake.

 

Disagree…

The pump has a check valve in the outlet that is there to allow fuel to only flow one way through the pump. This maintains pressure with the pump off and decreases the work the pump has to do to maintain pressure while running. If everything worked fine before you swapped pumps and now the pressure drops quickly (it’s supposed to hold for something like 30 min, but few do without dropping some, if I remember right mine drops about 5psi within the first 5 min and then slowly from there…) and is slow to gain pressure you probably have a jammed check valve in the pump (50/50 shot that it came that way vs you got some crud in there while swapping pumps that is keeping it from closing.

This is usually the cause of pumps new pumps that don’t want to pump a consistent pressure either, which unfortunately is not that uncommon with the walbro pumps (2 out of the 4 that I’ve messed with in the last 3 years came like that)

When regulators fail that worked in the first place usually the diaphragm gets a pinhole in it and the fuel leaks into the vacuum side, dumping into the intake (simple check, pull the vacuum line and see if there is fuel in there). If it’s a problem with the plunger sealing in the regulator it usually does it from day one.

Fuel injectors are not easy to jamb open suddenly. It’s next to impossible to get contaminants to the pintle/disk assemblies that are able to hold an injector open (inline filter & injector inlet screens prevent that), so the way it usually happens is from contaminants getting in them from the intake side or getting baked on by the exhaust gasses in the intake during the overlap period. IE, it doesn’t happen suddenly unless you do something dumb.

If in doubt, disconnect the fuel line from the rail assembly and dead head it with a gauge installed (make an adaptor to mount the gauge in the end of the fuel line. Click the key on for a second to let the pump run for a second or jumper the pump pin on the aldl connector). You should be able to deadhead the pump to something between 100-135psi, and the pressure should stay up for a while after you turn the pump off. If either doesn’t happen it’s pointing at a pump or pulsator problem (well, or a leaking fuel line, but you should have noticed that by now), either way you have to drop the tank to fix it.

The next time around throw away the pulsator and replace it with some high pressure FUEL INJECTION hose.

 

USUALLY, if they’re working right when you key on, you hear the pump going for maybe 2 seconds and then suddenly the guage needle will move to whatever the regulator bypasses at and stays there. I’ve seen empty fuel systems after they were just assembled needing 2-3 key ons before it gets a consistent reading, but after that _it should_ do it consistently with just one key on…

 

Wow. thanks for the info. I am taking everything on this thread into consideration. I will be reading again and again to make sure I understand what may be causing the problem.

I appreciate you time and help. --Dan