Need help on 89
Thread Starter
Le Mans Master
Joined: Dec 2006
Posts: 5,154
Likes: 2
From: Ft Myers Florida
Need help on 89
1989 Corvette, started idling eratically. Would idle to high for awhile, and then drop down to normal then high etc. Sometimes won't start when hot unless you hold gas to floor. Slight hesitation when hitting the throttle. Can't find any disconnected vacuum lines, sprayed wd-40 around intake gasket with no idle change, Fuel pressure was a solid 38 lbs going over 40 lbs when you hit the gas. Short of a compression test there is no oil in the coolant vice versa, no white smoke. New plugs cap and rotor, timing was good (was doing it before) no Check engine light.
Any ideas?
Any ideas?
Drifting
Joined: Aug 2002
Posts: 1,775
Likes: 125
From: Birmingham AL
Does the fuel pressure hold for a while after shutting down or does it drop off immediately? My regulator developed a leak and caused a major fuel leak through the vacuum line into the plenum. This caused hard starting after initial startup due to flooding. Not to mention running a bit rich. Pull the little vacuum line on the regulator and see if gas is in there (ignition off of course).
Thread Starter
Le Mans Master
Joined: Dec 2006
Posts: 5,154
Likes: 2
From: Ft Myers Florida
Does the fuel pressure hold for a while after shutting down or does it drop off immediately? My regulator developed a leak and caused a major fuel leak through the vacuum line into the plenum. This caused hard starting after initial startup due to flooding. Not to mention running a bit rich. Pull the little vacuum line on the regulator and see if gas is in there (ignition off of course).
What should it do?
Drifting
Joined: Aug 2002
Posts: 1,775
Likes: 125
From: Birmingham AL
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Drifting
Joined: Aug 2002
Posts: 1,775
Likes: 125
From: Birmingham AL
Pull the connectors one by one with the ignition off and check the resistance with an ohmeter across the 2 terminals. Make sure that they are all near 16 or 17 ohms. Check with the motor cold and then warm to see if there is any difference. One being really different (low) than the others would be a dead give away.
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Since you mentioned having to hold the pedal to the floor to start it, I would first check the injectors as described. They all should ohm very close to each other and all over 10 ohms. If one or more is way off in resistance, replace them all.
Le Mans Master
Joined: Aug 2003
Posts: 9,884
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From: Magnolia Mississippi
St. Jude '03-'04-'05-'06-'07
Le Mans Master
Joined: Jan 2003
Posts: 5,858
Likes: 7
From: Santa Maria CA
Ohming the injectors only tells you part of the story. You won't know if they are leaking without a visual inspection under fuel pressure.
I would start by hooking up a fuel pressure guage to the fuel rail, and take a look at what the fuel pressure is doing. This will tell you if you have correct fuel pressure, and if the pressure is holding or not.
I would start by hooking up a fuel pressure guage to the fuel rail, and take a look at what the fuel pressure is doing. This will tell you if you have correct fuel pressure, and if the pressure is holding or not.
Team Owner
Joined: Jan 2003
Posts: 20,322
Likes: 249
From: Summerland B.C. Canada
Start with fuel pressure tests. 
Burning Brakes
Joined: Dec 2000
Posts: 1,161
Likes: 0
From: Orangeburg, NY
to check the injectors, pull the connectors one by one with the ignition off and check the resistance with an ohmeter across the 2 terminals. Check the injectors when cold and when hot. The resistance should be 15 ohms for each one. There should be no significant (1-2 ohms) variation between then. If there is, it is time for new injectors. Have you checked the fuel filter, bad gas, low fuel in the tank?
Thread Starter
Le Mans Master
Joined: Dec 2006
Posts: 5,154
Likes: 2
From: Ft Myers Florida
OK got a chance to work on it today and here is what we have.
With accessory on engine off, fuel pressure is 42 lb
Running it is 39lb and quikly goes to over 40lb when you hit the throttle.
When Engine off it holds pressure wether having just run or just when the accessory was on.
No fuel in the Pressure regulator vacuum line.
When 10-15 inch of vacuum applied to regulator pressure drops a couple lbs and holds.
Now here comes the injector ohms. Numbered with cylinder number.
Cold, Hot
#1, 16.6, 17.1
#3, 16.7, 17.3
#5, 16.5, 16.8
#7, 14.2, 12.8
#2, 16.8, 9.0
#4, 16.7, 16.9
#6, 16.7, 16.9
#8, 16.7, 17.2
So I seem to have two bad injectors? What do they physically do when the resistance is too low?
I did take the F.I apart and pressurized the system and none of the injectors leaked.
So is that it? the injectors?
With accessory on engine off, fuel pressure is 42 lb
Running it is 39lb and quikly goes to over 40lb when you hit the throttle.
When Engine off it holds pressure wether having just run or just when the accessory was on.
No fuel in the Pressure regulator vacuum line.
When 10-15 inch of vacuum applied to regulator pressure drops a couple lbs and holds.
Now here comes the injector ohms. Numbered with cylinder number.
Cold, Hot
#1, 16.6, 17.1
#3, 16.7, 17.3
#5, 16.5, 16.8
#7, 14.2, 12.8
#2, 16.8, 9.0
#4, 16.7, 16.9
#6, 16.7, 16.9
#8, 16.7, 17.2
So I seem to have two bad injectors? What do they physically do when the resistance is too low?
I did take the F.I apart and pressurized the system and none of the injectors leaked.
So is that it? the injectors?
Last edited by Y-ME; Aug 23, 2007 at 03:05 PM.
Burning Brakes
Joined: Dec 2000
Posts: 1,161
Likes: 0
From: Orangeburg, NY
Time to replace the injectors, #2 and #7 are bad. there are many posts on this particular issue to review. The common thread is to get ones that are flow tested, to ensure consistency between. I am going to tackle this job as a winter project. I think I will be going with ##22 Ford injectors. they seem to be favored by some members, and I want to keep the car as close to stock as possible. I know they are Fords, but they don't have the logo on them.
Thread Starter
Le Mans Master
Joined: Dec 2006
Posts: 5,154
Likes: 2
From: Ft Myers Florida
Time to replace the injectors, #2 and #7 are bad. there are many posts on this particular issue to review. The common thread is to get ones that are flow tested, to ensure consistency between. I am going to tackle this job as a winter project. I think I will be going with ##22 Ford injectors. they seem to be favored by some members, and I want to keep the car as close to stock as possible. I know they are Fords, but they don't have the logo on them.
Le Mans Master
Joined: Jun 2006
Posts: 5,642
Likes: 5
From: One day you're a Comet...the next day you're dust... Arkansas
I don't get how buying Ford injectors is staying close to stock. There are many injector manufacturers in the market place. Bosch, Rochester, Accel, Standard Motor, Etc, Etc. Stock for 1989 was Rochester which don't have a good reputation here, but mine work fine.
Melting Slicks
Joined: Apr 2002
Posts: 2,118
Likes: 0
From: St. Charles, MO Route 66 Corvette Club
Y-ME: The spec for a Multec resistance is 16.5 +/- .3 ohms and all eight injectors should be very close to the same value. If you have an injector with a low resistance, that injector will inject a lower volume of fuel during the pulse width time from the ECM. Hope this is helpful.
Burning Brakes
Joined: Dec 2000
Posts: 1,161
Likes: 0
From: Orangeburg, NY
I believe the 89 had Multec injectors which had some problems, and some reconditioning services will not rebulid them. Some post indicated the Ford #22 and #24 are close to the oem, and have been reliable. Ford is not GM (as I joked) but when I said I wanted to keep the car as stock as possible I was referring to no major modifications