MAP sensor questions...
Thread Starter
Supreme Member
Joined: Jul 1999
Posts: 1,431
Likes: 1
From: Huntsville, AL
Car: '00 Chevrolet Corvette
Engine: LS1
Transmission: 4L60E
Axle/Gears: 2.73
MAP sensor questions...
I can't get my car to start, when you crank it the fuel injectors spray too much and drown the engine. I have become suspect of my MAP sensor. It reads 4.74 volts just sitting there. When you crank the car it drops to about 4.5. Does this sound right? The tube is clear and has no leaks.
-Mark W.
'88 SC Camaro w/ 305 TBI
-Mark W.
'88 SC Camaro w/ 305 TBI
Supreme Member
Joined: Jul 1999
Posts: 18,457
Likes: 16
From: Loveland, OH, US
Car: 4
Engine: 6
Transmission: 5
The MAP sensor's information is not used when attempting to start the engine. Therefore a bad MAP sensor cannot cause a no-start condition. Run like hammered dog plop once it starts, and even die, yes; no-start, no. The numbers for its reading that you gave sound fairly believabele to me. Start looking elsewhere for the cause of the symptom.
If you have fuel but the motor doesn't start, you probably have no spark. You can disconnect the injector lead and spin the motor over to clear any excess fuel. But it sounds to me like you probably have an ignition problem.
There's obviously more to this than you're saying in this post: what happened right before the car suddenly wouldn't start?
------------------
"So many Mustangs, so little time..."
ICON Motorsports
If you have fuel but the motor doesn't start, you probably have no spark. You can disconnect the injector lead and spin the motor over to clear any excess fuel. But it sounds to me like you probably have an ignition problem.
There's obviously more to this than you're saying in this post: what happened right before the car suddenly wouldn't start?
------------------
"So many Mustangs, so little time..."
ICON Motorsports
Thread Starter
Supreme Member
Joined: Jul 1999
Posts: 1,431
Likes: 1
From: Huntsville, AL
Car: '00 Chevrolet Corvette
Engine: LS1
Transmission: 4L60E
Axle/Gears: 2.73
I'll give you the whole story...
A long time ago in a driveway not too far away I installed a set of ported aluminum L98 heads, Torker II intake, 670 Holley TBI (with 65# injectors), and roller rockers on my 305. After getting it all put back together the car started and ran fine...unless you quickly opened the throttle and then it would lean out and backfire through the intake. After ensuring that everything was in working order it was determined that it was the stock chip not being correctly programmed for my modified engine that was causing the problem. I then swapped to a 7747 ECU (from an 8063) and bought all the stuff necessary to begin programming my own chips. Alas, I never quite got the ECU swap to work (after a few months of trying) and went back to the 8063. After swapping back the car would run, but it would run rough. Just for ***** and giggles I put the stock injectors back on top of the throttle body just to see how it ran with those. It really didn't make much of a difference. I put the Holleys back on it and now it won't start. This is the same thing that it did with the 7747...It's spraying fuel like a crazy s.o.b. It acts like it wants to start, but it just can't stay going for more than a split second.
-Mark W.
'88 SC Camaro w/ 305 TBI
A long time ago in a driveway not too far away I installed a set of ported aluminum L98 heads, Torker II intake, 670 Holley TBI (with 65# injectors), and roller rockers on my 305. After getting it all put back together the car started and ran fine...unless you quickly opened the throttle and then it would lean out and backfire through the intake. After ensuring that everything was in working order it was determined that it was the stock chip not being correctly programmed for my modified engine that was causing the problem. I then swapped to a 7747 ECU (from an 8063) and bought all the stuff necessary to begin programming my own chips. Alas, I never quite got the ECU swap to work (after a few months of trying) and went back to the 8063. After swapping back the car would run, but it would run rough. Just for ***** and giggles I put the stock injectors back on top of the throttle body just to see how it ran with those. It really didn't make much of a difference. I put the Holleys back on it and now it won't start. This is the same thing that it did with the 7747...It's spraying fuel like a crazy s.o.b. It acts like it wants to start, but it just can't stay going for more than a split second.
-Mark W.
'88 SC Camaro w/ 305 TBI
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