1990 Deville...No fuel to rail.

[charlie]

I just recently put a new fuel pump, ECM and relay switch in this car. It had been sitting for a year because I suspected ECM and/ or fuel pump trouble and did not have time to deal with it until now. I first replaced the fuel pump because I had no fuel in the rail. Then, I replaced the relay for the fuel pump knowing that the new pump was not running yet. Then, I repalced the ECM, according to what I was reading in forums my Cadillac Shop Manual, this may be the problem. I am not getting any codes after I replaced the pump (I guess because I had unhooked the negative terminal of the battery for a several hours while I removed the fuel tank?). I have checked the voltage to the pump at the harness connector by the fuel tank, I get 12 volts for about 2 or 3 seconds, then nothing, this verifies to be the situation at the relay switch also as when I turn the key to the run position I can feel the relay click on, 2 or 3 seconds later it clicks off. I just noticed that now....I am not getting any display at the climate control center, nor at the fuel data center. It is over 100 degrees today, and I know the heat is not good for computers. I have checked the ground wire coming off the battery and silicone greased it, I even ran an additional ground wire from the battery to the engine block to be sure I have a good ground. Last year I replaced the distributor, cap, plugs, rotor, ignition module, and rotor. I can get it to fire when I puor some gasoline down her throat. Any experts out there that have any ideas of what could be wrong? Thanks, Charlie

[Dave Shepherd]

The prime circuit for the pump operates as expected, 2-3 seconds prime then engine should start, then the pcm picks up the ball from there.  So check fuel pressure at the rail during the prime event, get or use a gage, remember when replacing the pump it may take 3-5 prime cylcles to get sufficient fuel to the rail.

[Porter]

Replace the OPS ( oil pressure switch ) , a mechanical switch device and you won't get a code for a bad OPS. Nor will the ECM recognize the problem either. At least with my experience - SBC-TBI , same year GM product.

Just went through this exercise with my 90 SBC - TBI last year.

HTH and good luck ,

Porter 

[charlie]

Replace the OPS ( oil pressure switch ) , a mechanical switch device and you won't get a code for a bad OPS. Nor will the ECM recognize the problem either. At least with my experience - SBC-TBI , same year GM product.

Just went through this exercise with my 90 SBC - TBI last year.

HTH and good luck ,

Porter 

Hi Porter, I never had any lights come on for oil pressure. Did you go through all that I have described, or just some of the same symptoms? Thanks, Charlie

[charlie]

The prime circuit for the pump operates as expected, 2-3 seconds prime then engine should start, then the pcm picks up the ball from there.  So check fuel pressure at the rail during the prime event, get or use a gage, remember when replacing the pump it may take 3-5 prime cylcles to get sufficient fuel to the rail.

This circuit has been switched on and off 50 times since I replaced the fuel pump, still no pressure at the rail! Thanks, Charlie!

[Porter]

Hi Porter, I never had any lights come on for oil pressure. Did you go through all that I have described, or just some of the same symptoms? Thanks, Charlie

Charlie,

I was going to delete my posted comment here - too late.

Take this over to the other forum where the real late model Cadillac technicians are.

My problem was the OPS and my comments here will be left for the record.

Some basic troubleshooting and we'll get you running in no time. Have to check all your fuses first, etc.

Porter

[charlie]

Yes, I have checked all fuses and relays in both the driver's side fuse block and the passenger's side. Thanks, Charlie

[harvey b]

Hi all,i do not know a lot about these cars,could it be related to the security system?,sometimes they will shut down the fuel pump if it thinks it is armed?,also the new pump is it a good one?,possibly the pump may be bad,check to see if you have power at the plug by the tank,some times you can whack the tank by the pump and they will start working?.not much help i know but something to try. Harvey b

[charlie]

Hi Harvey b, This year Caddy's security system shuts off the power to the engine cranking system, the starter will not even engage if antitheft is overridden. I don't have that problem, it cranks, I just don't have any fuel.  Thanks, Charlie 

[charlie]

Harvey b, I forgot to reply on the fuel pump....It was a brand new one, not a junk yard part. I did, however, notice that the old pump was a bit rusty and the resistor also had some rust on it. I wire brushed all the terminals and the resistor and coated the resistor with a fuel tank sealer to prevent any further rust. I also flushed out the tank and dried it throughly before re-installing it. I am not sure if the resistor was good though, I had no way of testing it and it was welded to the line assembly, so I could not just replace it without replacing the whole assembly- not available in auto parts stores. Thanks, Charlie.

[Ohio57-62Sedan]

Only Dr. John & his crew can help you out Charlie... The rest are swinging in the dark... Dr.J is ASE certified.. and so is most of his crew.. Certified that is...

[charlie]

Dr. John........where are you???

[Dave Shepherd]

Hmm, no one here knows 90's Cadillacs, lets see where did I put my ASE Master cert. paperwork.  If you look a a wiring diagram, the op switch is wired in series with the relay, if the relay fails the switch will take over fuel pump operation.  Try grounding the gy wire on the oil sending switch see what happens.  BTW, until the picture is clear as to what else may or may not have been checked, no one has any way to suggest where the issues may lie .

[hedgehog8]

Hi Dave, Sorry I took so long, had to find the op switch in my manual, then remove air intake assembly. I have grounded the grey wire, still no fuel to rail. I am beginning to believe that they may have given me a bum pump??? What do you think? I have also posted more info on the misfits site. Thanks, Charlie

[chalrie]

Geees Dave, I did what you suggested, like I said in previous post, no results. I did think I heard a fuse blow when I turned the ignition on though. I checked the fuses again, and your suggestion blew out the 20 amp fuse for the fuel pump. Thanks, at least I know not to try that again! Charlie.

[Ohio57-62Sedan]

He must be a master alright... Don't ground another item out on your car!!! Unless you have a pocket full of money to dump into your car... GO Find Dr. John That dude know's His late model Caddy better than anyone else.. Or Milke Jones... everyone else is just strokin you...

Geees Dave, I did what you suggested, like I said in previous post, no results. I did think I heard a fuse blow when I turned the ignition on though. I checked the fuses again, and your suggestion blew out the 20 amp fuse for the fuel pump. Thanks, at least I know not to try that again! Charlie.

[Dave Shepherd]

Geees Dave, I did what you suggested, like I said in previous post, no results. I did think I heard a fuse blow when I turned the ignition on though. I checked the fuses again, and your suggestion blew out the 20 amp fuse for the fuel pump. Thanks, at least I know not to try that again! Charlie.

Charlie, sorry about, that my 90 diagram shows the gy wire as a inline pulsed gd from the pcm for the relay and/or op switch, not a 12v source, so it is wrong or of course the fuse would not have blown.

[Guidematic]

Harvey b, I forgot to reply on the fuel pump....It was a brand new one, not a junk yard part. I did, however, notice that the old pump was a bit rusty and the resistor also had some rust on it. I wire brushed all the terminals and the resistor and coated the resistor with a fuel tank sealer to prevent any further rust. I also flushed out the tank and dried it throughly before re-installing it. I am not sure if the resistor was good though, I had no way of testing it and it was welded to the line assembly, so I could not just replace it without replacing the whole assembly- not available in auto parts stores. Thanks, Charlie.

Resistor? You are not speaking of the resistor for the sending unit, are you? That should not have anything on it. That will create an open in the fuel sender circuit, indicating a full tank all the time.

Mike

[STDog]

Charlie,
Have you tried powering the pump at the connector and checking pressure at the rail?
The one you get 12V on for 2-3 seconds.

That would at least test the fuel pump and the lines to the rail.

Have you changed the fuel filter?


I'd disconnect the line at the filter and make sure I get fuel to the filter, then put the filter on the tank feed, and make sure I get fuel through the filter
Use a helper, and the prime function, or manually power the pump. You need the helper to turn the power off quickly so you don't spill lots of fuel, or get creative in how you power the pump, so you can observe the fuel flow and turn the pump on and off at the same time.