85 Eldorado--fuel pump removal from tank

bwrench:

It's not ( or wasn't) hard 20 yrs ago, but just gettin up (gettin down's easy) and working over your head with the car on jack stands--now that ain,t easy. I'm still not 100% convinced it"s the pump but I'm only reading 5 psi at the fuel line valve fitting just before it terminates to the throttlebody--the "in line" fuel filter has been replaced--and the 02 sensor but it won't idle (it starts fine, then revs to 1100/1200 rpm and back to idle--stumbles and the ECM tries to "save it" and revs back to 1100/1200 rpm--does this until it finally stalls. As long as you pump the throtle, it will run (not smooth) but it will rev to over 3k and hold. Kinda washes the "bad pump" theory in my opinion anyway. The vacuum reading isn't real good but then it's hard to get an accurate reading when the engine RPMs won't "hold still"- but I have checked (and repaired a/r) all of the vacuum lines , at least the obvious ones or the ones I could reach/find. Last time I had a problem, (an in-dash module was bad) it cost me $800 for the Caddy dealer mechanic to remove 2 screws--plug in the module (which I later found on e-bay "new" for $45.00. They even had the Balls to charge me $12.00 "disposal fee" and left the old module (about the size of a pack of smokes) layin on my front seat. ( I raised hell).

Anyway --love this old caddy--gift of a friend who "passed" but this problem is drivin me crazy- I refuse to just start "replacing" everything in sight until I finally stumble on the "fix". I've also worked (built) enough engines to know that it's probably a "control" or sensor problem.

Appreciate the info although I'm not happy with your answer.

Thanks again!

Donzi

you need at least 35psi to run the throttle body injectors pump needs changed

If you only have 4 psi, then you need a pump. The pressure specification for that TBI system is 9 to 12 psi.

bwrench:

I knew it was around 10/12psi--the point i'm reading is the valve just behind the throttle body--I don't see any other point to get a reading--but if that valve is on the return side 5psi would be bout right. What ya think ??

donzi

I have never seen a perssure test port on a return line. What would be the point in testing pressure on the return side? If you did have 5 psi on the return side, you would have a restruction somewhere between the TBI unit and the tank.

As you stated the pump is bad--with the return on the TB blocked as suggested by "Superman Engineer" the pressure did go up to 8 psi which made it idle just fine but the pressure is still too low and the pressure relief valve in the TB may be bad also since with it connected it only reads 2-3 psi and the vehicle won't idle.

Thanks again for the help!

Donzi.

Throttle position sensor...leastwise that what it was when my vehicle acted that way...before finally arriving at a stall then no start (permanently) condition. First -- even second -- TPS failures are to be expected by that age....

You are getting some not too correct information! Throttle body injection will run on 12 to 15 psi, but a sure test would be to test pressure and with the pump running clamp off the fuel return line and the pressure should climb to 50 psi or more! Doing this test will eliminate the possibility of the pressure regulator being the issue and not the pump. As for dropping the tank it is rather simple and the job only pays an hour and a half! Not anything too rough to do.

Engineering Superman:

Thanks--"Block return to test pump"--My brain wasn't working that day--I've been leaning to the regulator from the beginning but hated to start tearing down the TB if it wasn't necessary.

I'll try that in the AM and go from there !

Donzi

Engineering Superman:

I did block the return as suggested! the vehicle idles now just fine but with only 8psi

I guess I'll need to replace the pump and the "pressure relief" in the throttle body must be bad also because with the return connected it only has 3-4 psi and it won't idle.

Thanks to all who helped!

Donzi

I have yet to see a manufacturer who makes the job easier by providing an access panel in the trunk. Drop the tank...

Volkswagen, Saab, Volve are a few that put a pannel in the floor to access fuel pumps