1997 Cobra Starting Problem

by Paul
(Kansas city MO)

1997 Ford Mustang Convertible

1997 Ford Mustang Convertible

Question re 1997 Cobra starting problem:

Hi. I have a 1997 Cobra with 17000 miles.

It has a c&l mass air sensor, March underdrive pulleys, x-pipe, 4:10 gears and a Zex dry kit.

After installing a Walbro high flow 255 lph fuel pump and adjustable fuel regulator it is hard to start.

I tried a brand new stock fuel regulator also and it did not help. It will crank over 5 or 6 times and not start then start right up after that. It is like the fuel is not getting to the engine for a while!

Any ideas would help!


I'm going to give you some places to start diagnosing your 1997 Cobra starting problem. There are a number of possible scenarios that could cause this to happen and it's going to take some detective work to figure out which component or combination of components are the culprits.

The first question is, do you have the correct application for your car? There are two possible Walbro high flow 255 lph pumps for the 1997 Mustang, but only one is specific for the '97 Cobra , the GSS342-400-782.

If you have the correct pump, the next question, is do you have everything correctly hooked up and are all of you clamps tight, preventing any possible loss of pressure?

If these potential issues are fine, then it's time to take out your pressure gauges and see if you have any pressure problems at start up.

Check your shop/repair manual for key on engine off pressure at both the fuel pump and the pressure regulator. Either of these (high or low) could be an issue.

I should note here, as well, that these pumps are known for causing a too rich
condition at idle
, that's why typically you want an adjustable fuel pressure regulator. It may also be a cause for too rich a mixture at start up.

Assuming that there are no other issues, such as a malfunctioning crankshaft position sensor which can cause the same symptoms (until it won't start at all), and your pressure readings are within normal numbers, there are a few last things to check to resolve your 1997 Cobra starting problem.

Did you clean your tank before installing the new pump. Although pumps and fuel sender assemblies can look the same there are some slight differences. As well, placement back in the tank can put your new filter in a different location than the old one.

If your tank floor isn't clean, your new pump may actually vacuum up junk off the bottom of the tank and partially plug your new filter. Worst case scenario, you fully plug it and burn out your new pump.

Finally, are there any other possible restrictions in your hose or fuel line from installation?

Chances are, it's one of these, or some combination of them that are causing your hard starting issue.

One last thing you can do, is assuming you still have your original parts, remove all the new stuff and reinstall your old parts to see if this cures the problem.

While it's rare, it is possible that you have a defective new fuel pump. Using process of elimination can be helpful, when combined with test gauges and factory specs to isolate the issue to either parts or installation.

Right now, you have too many variables and need to simplify the potential causes to cure the problem.

Hope that helps.

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problem solved
by: Paul

You were right about this one! My new fuel pump had a defective check valve.I bought a new 255lph pump from highflowfuel dot com and everything is fixed. The fuel pressure holds now and the car starts up perfect. Thanks alot!

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