Uh oh, LT1 97 didn't start. Options

[Steve91T]

So yesterday when I started the car, it cranked but didn't fire. It did start on the 2nd try. Odd, I thought. So then on m way home, I was steady at 35 mph when, for about a second, the fire went out. I had nothing. Then it came back and all was well. So I was thinking that maybe the opti was having a bad day.

Fast forward to today and the car wouldn't start. Cranked, but wouldn't fire....didn't even try. I noticed I couldn't hear the fuel pump priming. I banged on the tank with a rubber dead blow and tried again. This time I heard the fuel pump prime and the car fired, but then quit. That was the last time I could get it to fire. I also noticed the fuel gauge is pegged full.

Soooo, time to cut an access above the tank?

[mr.beachcomber]

So yesterday when I started the car, it cranked but didn't fire. It did start on the 2nd try. Odd, I thought. So then on m way home, I was steady at 35 mph when, for about a second, the fire went out. I had nothing. Then it came back and all was well. So I was thinking that maybe the opti was having a bad day.

Fast forward to today and the car wouldn't start. Cranked, but wouldn't fire....didn't even try. I noticed I couldn't hear the fuel pump priming. I banged on the tank with a rubber dead blow and tried again. This time I heard the fuel pump prime and the car fired, but then quit. That was the last time I could get it to fire. I also noticed the fuel gauge is pegged full.

Soooo, time to cut an access above the tank?

Not sure how the fuel pump management is carried out on a Camaro; however, with the '89 Vette there is a fuel pump relay that closes momentarily to prime the fuel rails. Once the oil pressure reaches 4 psi during cranking, another signal is sent to the ECM to close the fuel pump relay for normal start/run. The situation you described happens to early C4's all the time when 1) either the fuel pump replay is bad or 2) the ECM signal to run the fuel pump is bad (no fuel pressure when running once the engine is running). I've had the later case happen to me, and like you described, the Vette loses power momentarily until the 'limp home" mode kicks in to fire the fuel pump to restore power.

If you have good fuel pressure at the fuel rails, it's probably not the in-tank fuel pump. It's probably a loose wire or bad relay causing the problem. (I once serviced a customer's Vette that had broken electrical connectors inside the male side of the fuel pump relay that caused an intermittent "no start" situation. Had to re-terminated all the Weather Pak connectors for the relay. (Turns out the customer replaced the relay by pulling on the wires themselves when separating the components.)

Hope this helps!

[Steve91T]

Thanks. I'll check that stuff out first.

[CrashTestDummy]

Yep, start with a fuel pressure gauge, and work out from there. Most Opti's just quit. Start, no start, start, I'd look first at fuel pump, then grounds for the ignition, then coil.

[Steve91T]

Yep, start with a fuel pressure gauge, and work out from there. Most Opti's just quit. Start, no start, start, I'd look first at fuel pump, then grounds for the ignition, then coil.

I've had two opti' kick the bucket on me, and both times I at least got some bangs and pops. Like trying to start an engine with wires crossed.

This seemed like fuel. When it fired and quit, it acted like it was starved for fuel. Makes sense since I can't hear the fuel pump priming.

Can I get a fuel pressure test gauge at an auto parts store? Anything special that I need to look for?

[trackbird]

Not sure how the fuel pump management is carried out on a Camaro; however, with the '89 Vette there is a fuel pump relay that closes momentarily to prime the fuel rails. Once the oil pressure reaches 4 psi during cranking, another signal is sent to the ECM to close the fuel pump relay for normal start/run. The situation you described happens to early C4's all the time when 1) either the fuel pump replay is bad or 2) the ECM signal to run the fuel pump is bad (no fuel pressure when running once the engine is running). I've had the later case happen to me, and like you described, the Vette loses power momentarily until the 'limp home" mode kicks in to fire the fuel pump to restore power.

If you have good fuel pressure at the fuel rails, it's probably not the in-tank fuel pump. It's probably a loose wire or bad relay causing the problem. (I once serviced a customer's Vette that had broken electrical connectors inside the male side of the fuel pump relay that caused an intermittent "no start" situation. Had to re-terminated all the Weather Pak connectors for the relay. (Turns out the customer replaced the relay by pulling on the wires themselves when separating the components.)

Hope this helps!

I was just coming in here to add that information. However, I believe the oil pressure switch (for the fuel pump) is redundant (parallel) in the Camaro. Turn the key, the pump primes, start cranking and the fuel pump relay closes. If the relay is bad, when the car sees a few PSI (4-5?) of oil pressure, the oil pressure switch closes and turns on the fuel pump anyway. So, you tend to see extended cranking times, but the car will typically start if you crank long enough.

[Steve91T]

So no priming indicates a bad pump?

[trackbird]

So no priming indicates a bad pump?

No. No priming potentially indicates a bad fuel pump relay (or...obviously....a bad pump, depending if it runs and makes proper pressure when it does run). When you turn the key, the computer turns on the pump for 2 seconds to build pressure in the fuel rails, then it shuts the pump off until it sees you cranking the car. If the relay is bad, you won't hear the pump prime for 2 seconds (the ECM tells the relay to turn on....but it doesn't because it's "bad"). Then....after you crank it for a "while" (5-15 seconds), the oil pressure switch turns on the fuel pump and it will start.

The easiest way is to hook up a fuel pressure gauge and place it on the windshield. Turn the key on and see if you get pressure (2 second priming). Then start cranking. If you crank for what seems to be an extended period of time and suddenly the pump comes on...I'd test or replace the fuel pump relay.

[CrashTestDummy]

If you have to turn the key on, off, on a couple of times to get it to load up enough pressure to start, points to a pump. If it's not spinning up at all on key-on, that also points to a bad pump, but I guess it could also be a bad relay. I've rarely seen a bad relay, at least in the 94-96 Impala SS environment anyway. I don't have a lot of experience with the F-body LT1s, so those more-experienced will hopefully speak up here.

[Steve91T]

Yeah but not only am I not getting priming, I'm getting a no start condition. After beating on the tank, I turned the key and heard it prime. Then when I cranked it, it fired but quit, as if it was running off the prime only. That was the last time it fired.

I just went to the garage and tried again. Turned the key and heard nothing. Cranked the engine for a good 10 seconds and got nothing. Sounds like, from what you guys have said, it would take multiple failures of fuel pump relays to get a no start, not just extended cranking. Am I understanding that correctly?

The only other very weird thing is my gas gauge is pegged full. That must mean something. Where are the electrical connections for the gauge and pump?

[trackbird]

The only other very weird thing is my gas gauge is pegged full. That must mean something. Where are the electrical connections for the gauge and pump?

The connector should be plugged into the "bulkhead" in front of the differential (roughly where the seat back is for the backseat). If the gauge is pegged full, it may have lost the ground to the pump and fuel pressure sending unit (as I remember, no ground = "full"). The ground (as I remember) comes through the bulkhead between the back seats, over to the drivers side and under the door jam (likely clustered with the speaker wires) and then has a screw to the chassis under the drivers seat. That's going from memory, but I believe the LT1 cars were setup that way as well.

[Steve91T]

The only other very weird thing is my gas gauge is pegged full. That must mean something. Where are the electrical connections for the gauge and pump?

The connector should be plugged into the "bulkhead" in front of the differential (roughly where the seat back is for the backseat). If the gauge is pegged full, it may have lost the ground to the pump and fuel pressure sending unit (as I remember, no ground = "full"). The ground (as I remember) comes through the bulkhead between the back seats, over to the drivers side and under the door jam (likely clustered with the speaker wires) and then has a screw to the chassis under the drivers seat. That's going from memory, but I believe the LT1 cars were setup that way as well.

I know the ground you're talking about. That's the ground for the fuel pump and fuel gauge? I'll check it out this afternoon. I bet that's it.

[trackbird]

The only other very weird thing is my gas gauge is pegged full. That must mean something. Where are the electrical connections for the gauge and pump?

The connector should be plugged into the "bulkhead" in front of the differential (roughly where the seat back is for the backseat). If the gauge is pegged full, it may have lost the ground to the pump and fuel pressure sending unit (as I remember, no ground = "full"). The ground (as I remember) comes through the bulkhead between the back seats, over to the drivers side and under the door jam (likely clustered with the speaker wires) and then has a screw to the chassis under the drivers seat. That's going from memory, but I believe the LT1 cars were setup that way as well.

I know the ground you're talking about. That's the ground for the fuel pump and fuel gauge? I'll check it out this afternoon. I bet that's it.

I believe the gauge and pump use a common ground. That should be connected to both of them.

If that fixes it, I'm going to retire and hang up my remote diagnosis hat. (IMG:http://www.frrax.com/rrforum/style_emoticons/default/tongue.gif)


See, this is what happens when you start talking bad about that junkyard motor in there....it gets mad. (IMG:http://www.frrax.com/rrforum/style_emoticons/default/nutkick.gif)

[Steve91T]

The only other very weird thing is my gas gauge is pegged full. That must mean something. Where are the electrical connections for the gauge and pump?

The connector should be plugged into the "bulkhead" in front of the differential (roughly where the seat back is for the backseat). If the gauge is pegged full, it may have lost the ground to the pump and fuel pressure sending unit (as I remember, no ground = "full"). The ground (as I remember) comes through the bulkhead between the back seats, over to the drivers side and under the door jam (likely clustered with the speaker wires) and then has a screw to the chassis under the drivers seat. That's going from memory, but I believe the LT1 cars were setup that way as well.

I know the ground you're talking about. That's the ground for the fuel pump and fuel gauge? I'll check it out this afternoon. I bet that's it.

I believe the gauge and pump use a common ground. That should be connected to both of them.

If that fixes it, I'm going to retire and hang up my remote diagnosis hat. (IMG:http://www.frrax.com/rrforum/style_emoticons/default/tongue.gif)


See, this is what happens when you start talking bad about that junkyard motor in there....it gets mad. (IMG:http://www.frrax.com/rrforum/style_emoticons/default/nutkick.gif)

Haha so true. She must have found out that I've been researching LS1's.

[Steve91T]

(IMG:http://img.photobucket.com/albums/v199/Steve91T/Camaro/3A712340-1504-4670-AA19-55458253C545.jpg)

So the other day I'm running her ear off about my new Camaro. She then says, "Steve, do you realize we now have two Camaro's in the garage and neither one runs? How redneck are we?" Haha, so true. So I jumped in my old Camaro and turned the key, you know, just in case it happen to fix itself. It cranked, no fire. So one thing I noticed is my helmet blower wasn't working. I tapped that fan's power supply into the power seat wires. My electric drivers seat wasn't working either. So I pulled the driver seat and sure enough, my twist and tape wire job was coming apart. I now remember I ran out of proper connectors and so I just did a temporary splice. So I fixed the wiring. The seat works, my blower works and the car started. I still have no idea what the hell that has to do with the fuel pump, nor do I care (IMG:http://www.frrax.com/rrforum/style_emoticons/default/smile.gif)

[ar52kortlang]

The power seat and fuel pump share a ground located near the front seat

[trackbird]

Interesting....and a little scary. lol. I'm curious how those are related, but I'm glad you found it (and didn't have a fire in the process).

[CrashTestDummy]

Fuel pump and trunk light ground are common on a 94-96 B-body. And it's on the trunk lid hinge. So when someone complains about their Impala SS not starting, the common reply is: pop the trunk lid and see if the light comes on. Additional troubleshooting goes from there.

Good to know you go it fixed. Now fix it right!!

Not quite so yeller-tooth trailer-trash with one of those F-body's running, now are you? (IMG:http://www.frrax.com/rrforum/style_emoticons/default/2thumbs.gif)

This post has been edited by CrashTestDummy: Aug 1 2016, 01:47 AM

[Steve91T]

The odd thing is all I did was pull the insulation back just a little on the power seat wires and twisted the blower wires to them. So how that interrupted the ground is beyond me. The other night in used proper connectors.

You know maybe the actual problem is the ground under the seat is loose and me messing with the wires made a connection again. That's probably more likely. I'll pull the carpet up and check that ground.

[ar52kortlang]

When i had the cage and race seats put in they cut the floor mounts form the factory seats and ended by relocating the ground using a self taper..well after doing a run the screw loosened up... created resistance, heated up and caused the pump to quit working..