Injectors faulty?
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
Injectors faulty?
I've been reading a thread here about a car which has similar issues as mine.
Mine always feels like it's under load. It detonates and "sounds like a can of rocks" under hard acceleration. The CR is only a little under 9.5 I think (mechanic told me).
But, I have a rich fuel condition as well which made me think that being lean wasn't a problem, until I read that maybe an injector or two are going lean causing problems, and the other injectors and ECM may be over compensating making it lean.
It is also pulling 7 degrees of timing at WOT, all it pulls is 7, no more. I previously had some chip work done, but wasn't optimized for what it has now. Maybe they made 7 the maximum timing that the computer will pull.
So, to test the injectors, I read that I had to pull the harness off it and test the ohm's with a digital multi meter. I read to do this with a warm engine.
I have a super ram. Has anyone else tried this without having to remove anything?
Mine always feels like it's under load. It detonates and "sounds like a can of rocks" under hard acceleration. The CR is only a little under 9.5 I think (mechanic told me).
But, I have a rich fuel condition as well which made me think that being lean wasn't a problem, until I read that maybe an injector or two are going lean causing problems, and the other injectors and ECM may be over compensating making it lean.
It is also pulling 7 degrees of timing at WOT, all it pulls is 7, no more. I previously had some chip work done, but wasn't optimized for what it has now. Maybe they made 7 the maximum timing that the computer will pull.
So, to test the injectors, I read that I had to pull the harness off it and test the ohm's with a digital multi meter. I read to do this with a warm engine.
I have a super ram. Has anyone else tried this without having to remove anything?
Advanced
Joined: Jul 2004
Posts: 80
Likes: 0
I had the same problem with my 91, started to run a little ragged so I changed cap, rotor, plugs, wires, fuel filter, cleaned IAC. The more I did the worse it got! I read a note from Sam Lam on this Forum to check injector resistance: should be 16-17 ohms. I checked mine hot and cold, but there was almost no difference. They ranged from 5.0 to 18.0 ohms. Five of the 8 were bad and I ordered a set of 24# Accels from Summit at $229 + shipping (best price I could find). I started the installation last night and will finish tonight (if it doesn't rain). God, I hope this works. BTW, all the Accels checked out at 14.6 ohms on the bench. JFB tells me an impedance check will provide more information than resistance as an injector can have the correct resistance but still be junk. I pulled some technical articles from a few years ago and found GM had troubles with acidic fuels (particularly ethanol with a low pH) eating the insulation in the injectors and shorting them internally. Newer injectors don't let the fuel see the electrics. Hope this helps.
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
Thanks guys. Yeah, about 2 1/2 years ago I bought FMS 30# injectors. I'll try the resistance thing tonite with my multi meter. I looked at them today and 4 will be easy to check, the other 4 are partially covered by my super ram.
Team Owner
Joined: Jul 2004
Posts: 28,472
Likes: 3,290
From: Hartford WI
Take them off and send them to www.rceng.com and they will clean the things for you. Another way is to take it to a local tech college and see if they have an injector testor. I believe LPE offers the cleaning service for less than $100. Sometimes a clogged injector will cause a problem because instead of atomizing the fuel, it squirts it out. Either that or you could go with the Ford Motorsport ones which are 24 pph and have the EPROM reprogrammed which you will have to do anyways. Who did the EPROM for you?
I had the 30 pph ones with my Superram and had no problems but of course, that is when John was tuning it while playing with my car in Decatur, IN.
I had the 30 pph ones with my Superram and had no problems but of course, that is when John was tuning it while playing with my car in Decatur, IN.
Melting Slicks
Joined: Apr 2002
Posts: 2,118
Likes: 0
From: St. Charles, MO Route 66 Corvette Club
Hey guys: The GM injector problem will be found on 89 through 91 model years with the Rochester Multec injectors. These injectors are identified as being gray in color and will have the "RP" on them. If your injectors are a different color, they probably are not the 22 pound, stock GM injectors. Sometimes the injectors will test good until the engine warms up and then they short out. This is why you need to check the resistance both cold and hot. I may have contributed to my injector problems as I use a Techtron fuel injector cleaner often. I am pleased "my problems" has helped others.
Regards, Sam
Regards, Sam
Heel & Toe
Joined: Aug 2004
Posts: 21
Likes: 0
Originally Posted by Sam Lam
Hey guys: The GM injector problem will be found on 89 through 91 model years with the Rochester Multec injectors. These injectors are identified as being gray in color and will have the "RP" on them. If your injectors are a different color, they probably are not the 22 pound, stock GM injectors. Sometimes the injectors will test good until the engine warms up and then they short out. This is why you need to check the resistance both cold and hot. I may have contributed to my injector problems as I use a Techtron fuel injector cleaner often. I am pleased "my problems" has helped others.
Regards, Sam
Regards, Sam
My multecs test OK cold, but short when that warmed up, burning out my ECM
My shop blamed it on the injector cleaner I have been using. Don't use cleaner on the Multecs!
Drifting
Joined: Aug 2004
Posts: 1,448
Likes: 1
From: Tracy CA
'89 L98 104K miles.
Okay. Am I checking these wrong? I pulled the connector off the injector. Inside there are two spades. Meter is set on ohms. When I check the resistance across the two spades I read 0 ohms. Not .02. Zero. Did this with three injectors on a warm engine. All the same.
Am I stoned (not likely
!) or is this a bad sign.
BTW, they're grey... and, yes, I use the Techron stuff.
Okay. Am I checking these wrong? I pulled the connector off the injector. Inside there are two spades. Meter is set on ohms. When I check the resistance across the two spades I read 0 ohms. Not .02. Zero
. Did this with three injectors on a warm engine. All the same.Am I stoned (not likely
!) or is this a bad sign.BTW, they're grey... and, yes, I use the Techron stuff.
Last edited by EPiC Vette; Sep 18, 2004 at 03:55 PM.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Melting Slicks
Joined: Apr 2002
Posts: 2,118
Likes: 0
From: St. Charles, MO Route 66 Corvette Club
A reading of "0" ohms indicates a full short. If you car will run even if very rough.....you cannot have "0" ohms (in all eight injectors)......as this will not allow the injectors to place fuel in the engine. I would suspect you have your ohm/volt meter set to volts (instead of ohms) and you will get "0" volts when you measure across the injector. Make sure you are set up to measure ohms and try again! Oh yes.......I used the Techtron fuel injector cleaner too! I think this may have accelerated my problem. Rich at Cruzin Performance will not rebuild Multec injectors. Good luck!
Drifting
Joined: Aug 2004
Posts: 1,448
Likes: 1
From: Tracy CA
Had the meter set to ohms. Oh, yeah, I'm sure 
. I'm gonna check all of the injectors tomarrow.
Yeah, it's been running rough for a little while.
It just really threw me that the only three I check are fully shorted
.
Ah, but whattya gonna do?
. I'm gonna check all of the injectors tomarrow.Yeah, it's been running rough for a little while.
It just really threw me that the only three I check are fully shorted
.Ah, but whattya gonna do?
