1990 vette won't start!

JeffP1167

Well-known member
Joined
Dec 21, 2009
Messages
2,727
Location
Yucaipa, CA.
this has been a off and on problem where it sometimes starts then won't. Today it's having another bad day just cranks and no start! I depressed the fuel rail test port and a very minimal amount of fuel came out like maybe a teaspoon at the very very most. I am unaware of all the issues that could cause the fuel pump not to run so I took the pump out of the car and wired the grey wire to my positive battery terminal and the black wire to negative and couldn't hear the pump running.

Or is the purple wire the positive feed for the fuel pump?

Or do I just have a pump thats on it's last leg and it just died?
 
They had a thing on those cars called VATS, vehicle anti theft system....

it has a contact in the key those pellets that my '87 never gave a issue with, and so I had a chip in the computer under the pass side dash, and it eliminated the problem along with performance increases...

there is a realy that the computer activated to close contacts, AS I RECALL, and so that will disable the fuel pump, maybe something else....

all I know is that with my speed density system like from a '91 vette, meaning NO MAF sensor, that computer has a input that I trigger with a garage door opener receiver...that is MY anti theft system....I know, I"m a geek....

at any rate, when I activate that 5V regulator wire with my A/T system, that is what finally triggers the fuel pump for a second, to get pressure to start the car easy....

kinda a complicated setup for ME, but the computer could be wired totally Kosher on the hookup and with the Chip/CalPak programmed to eliminate VATS, the car acts normal....

well, normal for a VETTE, anyway....:clap::clap::):eek:
 
well, another 105.00 bucks into this mechanical @sshole !!!!! But it starts now so guess it could be worse !!!
 
Yes, probably VATS playing up. Not uncommon, 87 conv. here has the same issue. Sometimes it stats, sometimes it doesn't. The injectors won't fire, fuel pressure = OK. Confirmed to be the damned VATS module.
 
Yeah but everytime it doesn't start there is no fuel in the fuel rails. I just replaced the fuel pump and now it seems to start everytime. So I don't think my problem was VATS
 
That's why you should have a fuel pressure gauge you can hook up to the shrader valve.

#1 step in diagnosing EFI issues, know what the pressure is.
 
That's why you should have a fuel pressure gauge you can hook up to the shrader valve.

#1 step in diagnosing EFI issues, know what the pressure is.

A lo side off a HVAC gauge, or a old oil pressure gauge works fine, I have old oil gauge I use for my car....
 
But it won't hook up to the factory shrader valve, that valve uses a -4 sized 37 deg an flare connector, usually std pressure gauges come w/ npt hardware.
 
But it won't hook up to the factory shrader valve, that valve uses a -4 sized 37 deg an flare connector, usually std pressure gauges come w/ npt hardware.

Eh, I hard solder up all the fittings I need to make it work, one each a cut on the drill press, and some solder, done....

i'ts how I got that LT1 induction on the L98 engine, besides my buddy's TIG welding...

:smash::thumbs:
 
When I did do the fuel pump I did notice the fuel pumps sock was barely able to pass any fuel because it had this tan colored stuff caked on it (old fuel/rust) ?

Also when I did the head gasket I noticed the fuel rails also had this tan colored stuff in them. I have idled the car many hours so far probably have had two tanks of gas through it so far trying to flush the system out before I put my new 24lb injectors in the car. Have been idling the car with a new set of 19lb injectors I had.

I'm going to change the fuel filter next weekend, that probably is as bad as the rest of the system and a possible cause of low fuel volume in the fuel rails.

I didn't see any rust on the sending unit or inside the fuel tank so I think the sediment to be just bad gas that was in the car. It had sat for a year before I bought it.
 
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