Hidden Fuel Pump

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Jun 30, 2006 | 09:17 AM

#21

rick lambert

Le Mans Master

Joined: Oct 2003

Posts: 6,130

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From: seattle WA

I'd like to see a picture of the return line filter.....I've had my 87 seven years, and I haven't seen one.As for the sock in the tank (filter) replace it when you replace the fuel pump.

Jun 30, 2006 | 11:54 AM

#22

fast.asleep

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Joined: Nov 2004

Posts: 211

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From: Calgary Alberta

I'll get a fuel pressure gauge today. These injectors are almost 20 years old - than again so is almost everything on that car.

Quote:

Originally Posted by AKS Racing

I think you may be chasing the return line filter for no reason. The highest flow requirements for the return filter is when the car is at idle and the engine is returning most of the fuel. When accelerating, less fuel is returned to the tank, thus the load is less on the return filter.

Aaron

The problem shows itself only when I'm accelerating from idle (full stop) and only if I give 3/4 to full throttle. If I anticipate the problem and gently give gas to get rolling then punch it she accelerates fine. Since it is so close to idle I was thinking return filter - that and the thing has never been changed

I drove it last night and was easily able to duplicate the problem - I think it's slowly getting worse. It used to happen once in a while but now it is fairly constant. It feels like the fuel stops flowing for a second when I take off. I've experienced a very similar problem in my other car when I did not give enough gas before I engaged the clutch and the vehicle was left in 3rd or fifth - problem is the Vette is an automatic

I found this but it only seems to apply to cars with manual tranny's:

Quote:

Service Bulletin Number: 87-278-6E
Bulletin Sequence Number: 055
Date of Bulletin: 8803
NHTSA Item Number: SB000517
Make: CHEVROLET
Model: CORVETTE
Year: 1987
Component: ELECTRICAL SYSTEM:IGNITION:ELECTRONIC CONTROL UNIT
Summary: ENGINE DRIVEABILITY(IDLE STABILITY, TIP-IN HESITATION)-NEW SERVICE PROMS, REFERR ED TO AS MEMCALS RELEASED-ALL 1987 CHEVROLET CORVETTE MODELS WITH MANUAL TRANSMI SSIONS DJ

If nothing else I'll be giving it a tune up this summer anyway. I'm hoping one of these fixes the problem (spark plugs, cap/rotor, fuel filters etc)

I'll report my readings from the fp gauge after the weekend.

thanks all

Last edited by fast.asleep; Jun 30, 2006 at 11:58 AM.

Jun 30, 2006 | 12:23 PM

#23

fast.asleep

Thread Starter

Instructor

Joined: Nov 2004

Posts: 211

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From: Calgary Alberta

From what I understand if the problem is caused by faulty injectors the fuel pressure reading should be fine, correct?
What is the best/easiest way to test the injectors without pulling them?

Jun 30, 2006 | 01:36 PM

#24

rick lambert

Le Mans Master

Joined: Oct 2003

Posts: 6,130

Likes: 2

From: seattle WA

If the injectors, fuel pressure regulator and fuel pump check valve are all ok, you shouldn't see a fast pressure loss i.e. my pressure was at 41, after 10 minutes 36-38 and actually held there for about 30 minutes, that's great.

You can get a noid light to make sure the injectors are all getting a signal. You can use a digital voltage ohm meter to check injector coil health, they should read around 16 ohms +- I think .075, they should all be close, if any are way lower you've found a bad inj. coil. and the pressure tests, after eliminating the FP and FPR will tell you if they're leaking. Not necessarily tell you if they're dirty.

Jun 30, 2006 | 01:53 PM

#25

RRT vette

Le Mans Master

Joined: Feb 2006

Posts: 8,753

Likes: 9

From: Louisiana

Quote:

Originally Posted by fast.asleep

From what I understand if the problem is caused by faulty injectors the fuel pressure reading should be fine, correct?
What is the best/easiest way to test the injectors without pulling them?

Rick is correct. A fuel pressure guage you will need. With faulty/leaky injectors the pressure will not hold and will find the easiest way out. You can ohm them for one test and pressure test them. One sure way of knowing is to take off the plenum (for L98) and take the 4 hold down bolts out and pull the fuel rail with injectors still on and hold them over the holes and pressurize the system. If one leaks you will see it.

Jun 30, 2006 | 03:39 PM

#26

Blownfuel1

Racer

Joined: May 2006

Posts: 286

Likes: 0

From: Alpine California

Quote:

Originally Posted by fast.asleep

I'll get a fuel pressure gauge today. These injectors are almost 20 years old - than again so is almost everything on that car.

The problem shows itself only when I'm accelerating from idle (full stop) and only if I give 3/4 to full throttle. If I anticipate the problem and gently give gas to get rolling then punch it she accelerates fine. Since it is so close to idle I was thinking return filter - that and the thing has never been changed

I drove it last night and was easily able to duplicate the problem - I think it's slowly getting worse. It used to happen once in a while but now it is fairly constant. It feels like the fuel stops flowing for a second when I take off. I've experienced a very similar problem in my other car when I did not give enough gas before I engaged the clutch and the vehicle was left in 3rd or fifth - problem is the Vette is an automatic

I still don't think the return filter could be your problem, just because it's on the return side of your engine. If it was plugged, you'de have more fuel available at the injectors, not less, and from personal experience, it takes a LOT of extra fuel to cause a hesitation. Lean would be more likely to result in a hesitation like you describe. An arcing plug wire/ fouled plug COULD also cause this just off idle, but then as soon as the spark energy increase's, it goes away cause the spark starts jumping the plug gap again. I'd agree with exactly what your already planning to do, tune it up, and get a fuel pressure gauge on it. That should give you a better direction to look in.

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