Help! fuel problems

[butch001]

hi all another newbie with vette problems. i have a 91 rag top trying to bring back to life. I had it running long enough to have new top put on and bring allmost home on its own power but had to flat bed it the last mile home. have not had it running since. i checked spark (got it) -changed fuel filter- put fuel pressure gauge on it ( no pressure). did the ALCL-G test thing with no go. went to gas fill took it down to fill neck to get at the wire connector unpluged it checked voltage and was surprised. the voltage ranged from 11.75v down to 9.78v down to 8.50v voltage went up and down i had 12.49v at the battery. i found the #1 fuel pump relay going to put new one in. is there a #2 relay if so where?turned engine over no pressure.i could use some / a bunch of advice on this one. thanks in advance butch001

 

[strokin383-c4]

There should only be one relay located on the driver's side firewall above the battery. Check your fuel pump. it may be dead.

 

[boomdriver]

You WILL see varying voltage from the fuel tank sender wire assy...

remember, there is power to the pump, there is also reference for the level sender that will be anywhere based of gas level.

When people change the can fuel filter they have only done half the job. If the can was full of crap, the strainer is just as full. Dirt/rust has to go thru the strainer thru the pumpto get as far as the can. If it went that far there is a fair chance the pump is damaged or worn.

Pull the tank door off, then the tank access plate. Lift sender assy up and out. Be careful not to tweak the float arm or it wil never be accurate again.

Best to change the pump and strainer on the bottom. Siphon all the gas out and see what kind of trash and junk is still in the tank. I reccomend wiping it out as much as possible OR use the siphon tube to suck it out. However you choose, the dirt and crap has gotta go.

Re-assemble and test fuel pressure. needs to be key ON and get to 40 psi and hold that for near an hour and then slowly loose the remaining 35 psi over the next 6-10 hrs.

It sounds to me that there is a LOT more going on than you are describing. New vette owners have the worst time trying to describe what they see/hear from an engine they have no experience with. They don;t know if it is supposed to lope at idle, or if its really supposed to cold start idle up to 1100 rpm then go down to 600 by itself. They don;t know. Thats why we are here.

Before going further you will need these basic tools:

Fuel pressure gauge
Noid lites
DVM (volts, amp, ohms)
small dentist mirror on telescopic stem
Techs Stetiscope
spark tester
sm wire brush set
silicone ign grease
GM edition FSM with color electrical drawings

Follow the FSM flow charts for diagnostics. They are never off course.
Use only Delco ignition parts (electronic ign HEI, ESC etc)
Go back and set all sensors, tps, ck IAc for function and ck for vac leaks everywhere.

Once you've proven the basics to be ok, then you can start to look for the more exotic failures. Your wire harness is sh*t and probably part of the problem. Look for the harness tape unwraveling and coming apart. Thats where you find splices that are also coming apart....'
Read the FSM and familiarize yourself with the engines operating systems. What they are and how they operate. So when someone here says..." get a good thick layer of silicone ign grease under the ICM and be certain that none of the wires are being pinched..." You will know exactly what they are talking about,.

Try this stuff, note the results and get back to us. It will get there but it will take MUCH longer if you do not follow the FSM
guideline for diagnosing eng performance problems.
Above all, DO NOT attempt to apply 1979-80s mechanics to these cars. They do not do well when "bubba'd" and will usually end up so screwed up that some never get straightened out enough to become a DD. If Bubba approaches your car, CALL 911 and wait for help to arrive !
The Corvette is more complicated than a redneck with a beer in his hand.
Hope this helps in someway....My best advice...get and use that FSM..don;t waste any money on a haynes book or the other books from the parts store. Those are worthless. Junk.
Buy the real GM 2 book service manual and then you can repair the computer even if you're blind.

 

[strokin383-c4]

Nicely done Boom!

Haha glad there are people like you here to help.

Thanks,
Sean

 

[butch001]

hi guys and thanks the help. i really do appreciate that you will take the time to help others. i hope it does not take as long for you to type as it does me.

i started out searching for the fuel pump relay. could not find it acording to HAYNES and CHILTONS just was not there where they said! went to a dealer he told me it was a under the knee bolster driver side again (GOA) went to another dealer he said the relays are under the dash below the glove compartment. yup there it is a bank of 2 relays and a bank of 3 relays. they all look to be the same relay.
i was testing the voltage comeing to the fuel pump at the female connector and got varing voltage. never ran into this before
All this is further complicated because i belive this vette was a drug seizre car or was searched for drugs. when we got it last year my wife was vacumeing the vette and found a crack pipe stem with brillo in it ( we watch cops) and we were suspicious the way the dash was all loose and pulled back with wires and relays haning down. and the top was cut several places.
this could be some of the problems. not maney places to hide something.
ok now boomdriver i have all basic tools you listed but the NOID lites and GM2 FSM.
how maney noid lites will i need ? where is best place to get the FSM ?
and last what kind of fuel pump should i get and where.
thanks to strokin 383-c4 and boomdriver thanks again butch001

 

[boomdriver]

Noid lites,....those are cheap test tools to help see the inj signals. The parts store might have them to rent or a set for sale. Its a nice tool to have around these days with FI engines being the norm. Carbs on street cars are justn about a thing of the past...

The FSM.....do a search here for threads...there are several links to either a CD version or new paper back books..(like shop books) Cost varies...I paid $75 for the 2 book set for 1987 used from E-Bay. That is also your best source of hard to find parts... Many things are available at the parts store but the odd stuff is all over e-bay.
New FSM can sell for $150...so shop around a little. CDs are much cheaper but then you have to print out bunches of stuff sometimes. Books are nice to lay on the windshield and be able to flip thru the different sections. The older copies have the elect all in color exactly like the wires on the car so thats very nice. I've heard that newer books are B&W drawings.

The fuel pump,...if its a stock engine, the listed pump for that model will do. It can be had at most any parts store. Just make sure to have the warranty. Its easy to change. Be prepared to do some patchwork with fuel lines...
Taking 20 yr old fuel lines off antique nipples on the fuel sender assy usually means cutting. You have to have damn good fit with these lines because they are high pressure and leaks happen easily. The lines are steel tubing that have hose made on toward the end for clamping onto things, so the hose that you can cut off and re-use is limited. Get some new fuel inj clamps and maybe some injection hose that size to do any splices/repairs. I've had to use a brass barbed double nipple to add a few inches to a line. When you do the pump, also get a new tank gasket. The old one will come apart and thats a sure leak.