I have a 1991, automatic, L98 car that I have a question on regarding the fuel pump. I initially thought the injectors were leaking by, but after checking today they appear to be fine. I ohmed out the injectors, and they were all about 16.5, +/- .3 which is what a friend that works at a dealership stated they should be. With the fuel rail, and injectors lifted out of the intake, and the fuel rail pressurized, it read 41 psi on my gauge but quickly dropped from there after the pump shut off. None of the injectors were leaking by as I was able to visually confirm that. According to the service manual, I crimped off the pressure line, and the pressure held, as soon as I released my vise grips it dropped to zero. Also I replaced my pressure regulator as the pressure was about 35-36 psi, with the new regulator it is 41-42 psi. My question is if the pump is bad, or if it is the pulsator near the pump in the tank? The car runs fine, no hestitation, just poor starting as it cranks longer than it should, also the pump doesn't seem to be noisy, and no vibration which the manual states could indicate a bad pump. According to the service manual the three items it said should be checked were the pump coupling for leaks, the pulsator, and finally the pump itself. I appreciate any help, or suggestions!!!

 

It sounds like the check valve in the pump is bad. Your testing has narrowed it down. I'm not familiar with the location of your pulsator (mine is @ the fuel rail)....but my $ is on the check valve.

 

According to the service manual, it said it is in the tank near the pump, and diagram indicates such, but I haven't removed the pump yet to confirm this. I guess I might as well do that now, why not, I have taken just about everything else apart in this car in the last year. Oh yes, the car has 40500 miles on it if that matters. I guess a pump is cheaper than a set of injecters, but those are only about $300 for a set of Bosch's. Thanks for the quick answer!!!!

 

You bet. Seeing how you had the injectors out of the intake for a visual when pressurized , that takes a lot of the "guess" work out of it. While you are in there replace the sock (strainer) and check all the connections. Good luck.

 

Sounds like your check valve is ka'put. Thankfully replacing fuel pumps is simple in these cars.

 

I got the fuel pump, (Master), sock (or in tank fuel filter as the manual states), and the pulsator for $100.00, and Advance Auto had everything in stock. Well it was either $100.00 over the bar this weekend along with a hangover, or work on the redhead as my son calls it, LOL!! At least the car doesn't talk back, and when it gets the best of me , I cover it up, and shut the lights off in the garage!! Thanks again for the help guys!!!

 

my 85 has the same symptoms. I did the visual test of the lifted injectors, replaced the regulator, etc. Don't be quick to spend $$ on a new pump for a check valve. The pulsator is just ahead of the pump and I've been told that it can be removed and replaced for testing with a length of fuel hose and a couple of clamps. That'll be a cheap test to rule out the pulsator if that is your problem. I have not done this yet, but plan on doing in the spring. good luck and let us know what it turns out to be.