1990 - help
Thread Starter
2nd Gear
Joined: May 2013
Posts: 2
Likes: 0
From: rock hill sc
1990 - help
Have had 1990 Corvette for 3 yrs. All the sudden stalled on me one day. It will crank but not "catch". Thought was fuel filter or fuel pump. Got it changed out... no such luck.... Mechanic hooked up to computer it didn't throw any codes but he changed computer board out... started but only stayed running 2-3 minutes't.. His schematic book showed some type of chip should be under glove box, pulled out glove box only to find nothing under there. Used a diff set of keys thinking security chip on first set of keys died. Only stayed running 2-3 mins again. Anyone have suggestions before I have to tow to dealer and have to pay way too much?????
Race Director
Joined: Feb 2003
Posts: 16,475
Likes: 270
From: Kingman AZ
Cruise-In VII Veteran
Cruise-In VIII
St. Jude Donor '06-'07-'08-'09-'10-'11-'12-'13-'14-'15-'16
Obtain a shop manual and follow the troubleshooting guide for a "no start". Then you can find what the problem is instead of throwing parts at it.
If you go to the appropriate area of the Events and Regional section here then I bet you could get someone to help you work on the car so you would not have to pay the "Corvette Tax" at the dealer.
If you go to the appropriate area of the Events and Regional section here then I bet you could get someone to help you work on the car so you would not have to pay the "Corvette Tax" at the dealer.
Melting Slicks
Joined: Sep 2008
Posts: 2,376
Likes: 111
From: Cherokee National Forest TN
90 - 91 L98's use a speed density engine management system = no mass air flow as in early models.. Factory injectors are prone to failure, they are batch fire. If one injector fails/shorts all or some injectors will not work. Normally this is a heat related problem, runs when cold dies when warm/hot.
Ohm test the injectors w/cold engine then after it quits running to determine if there is an injector issue. 14 -16 ohms = normal.
Ohm test the injectors w/cold engine then after it quits running to determine if there is an injector issue. 14 -16 ohms = normal.
Thread Starter
2nd Gear
Joined: May 2013
Posts: 2
Likes: 0
From: rock hill sc
This is what has been done and still not running...
my mechanic has replaced fuel pump and filter ignition module, engine control module... runs for about 5 minutes then it loses injector pulse. Injectors are ok, the electronics stop sending a signal to them....
Racer
Joined: Oct 2006
Posts: 438
Likes: 14
From: Tucson/Santa Paula AZ/CA
2017 C4 of Year Finalist
Did "your mechanic" have a FSM? What were the resistance values of the injectors when it was in the failing condition. The "pulses" you refer to are actually a ground signal. The injectors should have 12V any time the ignition key is ON.
This site may help: http://www.corvettebuyers.com/c4vettes/l98.htm
if you disregard the bit about needing oil pressure to run the fuel pump. That is only true if the fuel pump relay fails.
Mick
Last edited by QZRBLU; Jun 4, 2013 at 03:59 PM.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
Wow that link is OLD. The guy who wrote it is no longer with us to correct all the errors it has in it. Bank fire? Uh-uh. I debunked THAT one...
There is no connection between the oil pressure sender and the ECM...
The injectors are synchronized to the rotation of the engine by the reference pulses coming from the ignition module in the distributor (the ECM also uses the reference pulses to know when to turn on the fuel pump). It sounds like you're losing these pulses. The ignition module gets VERY hot when the engine is running. It needs to have THERMAL (not dielectric) grease under it or it will stop working. Check for that.
When the engine stops running you should still see something on the tach while it's cranking. That will tell you that the ignition module (and the pickup coil) is working.
There is no connection between the oil pressure sender and the ECM...
The injectors are synchronized to the rotation of the engine by the reference pulses coming from the ignition module in the distributor (the ECM also uses the reference pulses to know when to turn on the fuel pump). It sounds like you're losing these pulses. The ignition module gets VERY hot when the engine is running. It needs to have THERMAL (not dielectric) grease under it or it will stop working. Check for that.
When the engine stops running you should still see something on the tach while it's cranking. That will tell you that the ignition module (and the pickup coil) is working.
Safety Car
Joined: Jan 2004
Posts: 3,556
Likes: 13
Circuit 458 from the output side of the pump relay and the OP switch also runs to pin Y20 on the '727 ECM which is the fuel pump input.
Not relevant to start up but the ECM has a table to adjust the inj pulse width in relation to voltage changes
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