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90 L98 won't start ~ Got Spark and 48 psi at the rail..

z34ls1

Active member
Joined
Sep 28, 2008
Messages
34
Location
Indiana
Corvette
2001 Quicksilver M6
Greetings Everyone, My name is Joe.

I've always been a F Body Guy till recently. My Dad had a '68 vette that he traded in 1993 for a low mileage '91 L98. I miss the '68 but my Dad passed away this February and I miss him more. A couple months ago my Mom sold me the '91 with 41,000 on it, she was tired of looking at it in the garage. I feel the same way she did now, the car is immaculate and I want it to stay that way.

Enter the '90 Vette I purchased last Friday from some friends facing foreclosure(I don't want to sound like a sniper waiting to snag it's next target). I got the Vette and they are current on their mortgage and got a few bucks extra to boot. The '90 had been sitting on a trailer in their Barn for about 3 years. It was parked for a number of reasons but mechanically the car's Fuel Pump had given up.

Here's where I started....

Put a new 800 amp battery in.
Attached Fuel Pressure gage to rail and found No Pressure(as Told)
Removed Fuel Pump
cyphoned Tank
Replaced Fuel Filter(let gas drip from lines before installing)
Replaced pick up screen, Pump, Gasket and reinstalled.
Tested Fuel Pump with ignition key on and maintained 48 psi.
Next tried to start and no Fire, tried a bit of starting fluid and it fired and then stalled right away.
Next I pulled 2 spark plugs from the drivers side and noticed both were black and dry.
Cranked Engine over with a plug grounded and noticed a weak spark.
Removed Coil from Distributer and found it was full of water.
Replaced Coil, Cap, and rotor, reattached all wires, 18436572
Checked for spark again now spark is very bright and consistant with engines rotation.
Reinstalled Plugs, tried to start and it sounds better but won't fire more than a hiccup.

Next........
Registered as a member here and read everything I could find on starting problems for a L98 and for Injectors not pulsing.

Next I jumped Terminals A and B and got nothing more than 12 12 12....12 12 12 good news I think but car still don't start.

Sequenced Code Recovery - 1990 through 1993: Jumping A and G
The following was displayed:

1.
C12

1.
---

4.
---

1.0 <--------- This is where it stopped

Please Help me, I read about fuses under the ECM. I assume that were are talking about the Massive amount of Fuseable Links located all around the battery tray?


Had to add this after reading more here.

I never checked to see if they removed the jumper pin. I found it was in and jumping AB while I had drained my battery trying to start the car. I read that if you try to start it with the jumper in it would damage the ECM.
*Note I pulled the codes but sequence code recovery never cycled through all the way.
 

jmccloud

Well-known member
Joined
Feb 1, 2003
Messages
694
Location
Maryland
Corvette
1995 White Coupe LT-1 Auto
No start

Welcome to a great site.
Sounds like your injectors are clogged or have failed. Check their resistance with the lead removed (I think 16ohms - use the 'search' function above to confirm). If they read ok, they're likely clogged from jellied gas since the car sat for so long. I've never cleaned them but there is lots of info in search.
I don't believe starting the car with the ALDL in diagnostic mode harms the ECM. I've got an old service manual for a '91 Regal I used to own and could look it up but you're better off with a Helms Factory Service Manual (FSM). The other manuals are of limited use. Be sure to get the correct year, red, two volume version. The white, single volume manual is a preliminary version.
Since the engine ran briefly with starting fluid, focus on fuel delivery - injectors.
Good luck
PS Disconnect the battery and charge it fully with a charger. The Corvette electronics (including diagnostics) won't function well with a low battery and even if the engine started, a low battery may damage the alternator.
 

z34ls1

Active member
Joined
Sep 28, 2008
Messages
34
Location
Indiana
Corvette
2001 Quicksilver M6
Thanks for the Reply. Last night it rained pretty good here, they are calling for more today so I may not be able to check then tonight. I will post my results as soon as I get them.
I read here that there is no cleaning the Injectors from this year car?

Once Again Thanks for the Information.

joe
 

z34ls1

Active member
Joined
Sep 28, 2008
Messages
34
Location
Indiana
Corvette
2001 Quicksilver M6
O.K. just got back from my lunch break and checked my Injectors ohms out.

I know from reading that 16 is roughly optimum, here are my results:

Drivers Side
11.3
16.0
16.2
8.2

Passenger Side
16.2
1.9 yeah that's right....1.9
16.2
16.3

So it looks as if 3 are Bad, is this keeping my car from starting?
 

jmccloud

Well-known member
Joined
Feb 1, 2003
Messages
694
Location
Maryland
Corvette
1995 White Coupe LT-1 Auto
No fuel

I believe your year utilizes 'batch fire' meaning that all the injectors on one bank fire together. Further, if one injector is kaput (low resistance) the computer will shut down that bank. There are some really helpful injector vendors, one is FIC Injectors (they support some forums but I'm not sure this is one of them). You likely need a set of new ones - much more reliable and not too many more $$ than tinkering with the old ones.
As a trouble shooting effort, you might try leaving the two really low reading injectors unplugged and try for a start; perhaps the 11ohm one too. Since the two low resistance injectors are on separate banks, they may be shutting off both banks.
Hope this helps.
 

Hib Halverson

Technical Writer for Internet & Print Media
Joined
Jan 10, 2001
Messages
13,452
Location
CenCoast CA
Corvette
71 04 12 19
I think it unlikely that all eight injectors could either suffer electrical failure of "clog up" all at the same time.

If this were me, I'd open up the 91 factory service manual to the part of Sec 6E that discusses "cranks but won't run" then I'd follow the diagnostic steps in the book.

Being that you've got fuel pressure and you have spark, I'm going to guess that there is a power problem in the circuits that feed the injectors. That kind of problem typically will not set a code.

Now, it is true that you may have one injector that has a coil problem, but given everthing else being normal, that should not prevent the engine from starting but it may make the engine miss.

Be very careful with "starting fluid". Yeah, it can help fire the engine provided there is spark, but the stuff is very low octane, causes massive detonation and can damange an engine if misused or used too much.

Lastly, when it comes to electrical troubleshooting, any aftermarket service manual is best used to line your catbox. The FSM, available from Helm, Inc.'s web site, is the only way to go.
 

z34ls1

Active member
Joined
Sep 28, 2008
Messages
34
Location
Indiana
Corvette
2001 Quicksilver M6
Hey thanks for the info on unplugging them, I was just reading that on another thread where the guy removed the wires to #8 injector which was bad. I got 1 very bad one on each bank, and a low one as well.

Time to fork out the $$ which is no big deal, I just want to hear it run before I pull it.

I may try unplugging the bad ones first and see what happens. I agree about replacing them all, after my Dad did the '91 it ran like a scared Rabbit.

Any Advertisers here wishing to PM me please.
 
Joined
Oct 7, 2007
Messages
719
Location
Amherst, NY
The L98 ECM signals 4 injectors at the same time. Right side injectors are wired in parallel, same for the left. If all four injectors on either side were ~16 ohms, then total resistance would be ~4 ohms. Swap in a one bad ~2 ohm injector, and the total resistance dropped on the passanger side to ~1.5 ohms. Can this cause a no start situation? The prior owner of my 1989 vette had the dealership replace all 8 injectors, 2 were low (one on each bank), but not as low as 2 ohms, and the car would not start. I would try disconnecting the 2 ohm injector first.
 

G Winter

Well-known member
Joined
Aug 21, 2004
Messages
2,177
Location
NW Iowa
Corvette
1990 red convert 6 sp
The L98 ECM signals 4 injectors at the same time. Right side injectors are wired in parallel, same for the left. If all four injectors on either side were ~16 ohms, then total resistance would be ~4 ohms. Swap in a one bad ~2 ohm injector, and the total resistance dropped on the passanger side to ~1.5 ohms. Can this cause a no start situation? The prior owner of my 1989 vette had the dealership replace all 8 injectors, 2 were low (one on each bank), but not as low as 2 ohms, and the car would not start. I would try disconnecting the 2 ohm injector first.

If memory serves me correctly, I read on this forum that a shorted injector(very low ohms) could cause the ECM to shut down the injectors on that bank. ;shrug I would try unhooking those two injectors. According to the FSM 10 ohms is exceptable ,but my feeling is if the ohms are dropping it is going bad and should be replaced.

Glenn
:w
 
C

chevylu

Guest
Try this:

Problem:
When it is cold, the engine consistently starts and runs reliably. After the engine comes up to operating temperature, when it is shut off, it will not start; it cranks but will not run.

Diagnostic Tests:
Following diagnostic chart A3 in the FSM
• No codes are present
• Good spark is present on all cylinders
• When the engine is cold, a noid light blinks reliably on cylinder 1; when the engine is hot, it will not blink
• When the engine is cold, a noid light blinks reliably on cylinder 2; when the engine is hot, it will not blink
• When the engine is hot, disconnecting the cylinder 2 injector will allow the engine to start; reconnecting it while the engine is running will cause the engine to stop running

Injector Resistance:
Cylinder Cold Engine Hot Engine
1. 16.7 17.3
2. 6.4 0.7
3. 12.6 8.9
4. 16.1 15.1
5. 16.8 17.6
6. 15.5 12.2
7. 15.6 12.1
8. 16.1 16.9

Conclusion:
Injector #2 shorts out completely when it is hot.
Time for a set of replacement injectors.
 

z34ls1

Active member
Joined
Sep 28, 2008
Messages
34
Location
Indiana
Corvette
2001 Quicksilver M6
I read the post above and want to say THANKS for all the Responses!

Before I read the Replies I got her fired up with the Great Helpof this Forum!
Here is what I did....
I started with the 3 bad ones unplugged, but it would not catch fire. It sounded so close so I plugged the next highest number in on the Drivers side and with a tad bit of throttle she fired right up. After she held her own idle I plugged the other one in on the drivers side and the idle picked up a bit but was still rough. After a few more minutes I went to the Passenger side and plugged in the only bad one on that side and she shut off.

I unplugged it, then refired the car back up!
It's running rough as heck, But it's Running!

I can't say Thank You Enough. Forums like this one are the Most Helpful.

I want to Post an Introduction post soon and I will, I promiss. I'm really into F Body's but the Vette's are in a class of their own. I own a '04 Z71 Avalanche, 2 95 Z26 Berreta's, a '92 Dale Earnhardt Z34 Lumina featured in the Link below, '95 Z28 with an '02 Doghouse mod, a '66 duece that I'm debating putting the L98 out of the '90 into. If I do that I'll be Selling off the rest of the '90 which has a nice Body but the crapiest paint job I ever seen.

On another forum LS1.com I have my Build thread that I would like to share with anyone that has about an hour to read through ---> http://www.ls1.com/forums/showthread.php?t=71662


I will be posting here often as I feel I have found a Great Site with Very Valuable Information. Thanks for Sharing Everyone.

Joe
 

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