chagger32

i been having issues with a 84 corvette i picked up the biggest problems i am having is code 42 and when i punch the gas there is a lag then it catches up and finally goes until another lag happens.
about 15 minutes into the drive as well my car cuts off on me sometimes leaving me stranded with the battery dead sometimes it gives me one more go at getting home before calling in a tow!



i just bought this car and i really would like to use it i have already replaced these items
1 - alternator
2 - radiator
3 - shocks
4 - battery
5 - fuel filter
6 - calipers and breaks
7 - oil and filter
8 - complete coolant flush

Silver85

Do you have a FSM? They are invaluable for troubleshooting. Work the flow chart and see where you end up

chagger32

code 42 points to a lot of things in the 84 service manual probably about 20 different things i am not experienced enough to run every test or know what to cut it down too for the problems i am having

Silver85

I don't mean this as harsh as it may sound but if working through a troubleshooting chart in the FSM is above your skill level, the best you can hope for is to start throwing random parts at it and hope you get lucky. Any local shade tree guys that might help you out? What tests can't you run?

corvette_realtor

You're sure it's a dead battery? None of the electrical components work when the car dies?

When I bought mine it would die after giving it a lot of gas (like going onto an interstate ramp) or just after driving for about an hour. It was the fuel pump.

If your battery is still dying after replacing it and the alternator then there is something drawing too much electricity I guess... Bad wiring. Sometimes the corroded battery cable ends need to be cleaned.

Maybe you need to service the spark plugs and distributor. I had new spark plugs, spark plug wiring, and distributor cap installed on my car prior to purchase. They probably thought that's what caused the car to die when it was actually probably the fuel pump.

Purple92

I'm far from an expert on the earlier C4's - but let's take things one step at a time.

First off - with the car running - check the voltage (at the battery) with a voltmeter. The voltage should be above 13.5 Volts - if it isn't the alternator isn't doing it's job, or you have a marginal connection somewhere in the system. .

Assuming that you have a functioning alternator - the next thing to do is to check the battery. I'd recommend taking it to a parts store that will test it for free (someplace OTHER than where you bought the replacement battery you recently installed). Assuming the battery tests good - fully charge it and re-install it. Next - prevent the car from starting by disconnecting the coil wire, and have a friend crank it while you measure voltage - a fully charged battery should stay above 11.5 Volts for at least 10 sec of cranking.

OK - assuming that your charging system is up to snuff - my $0.02 - the most likely cause for the problem you describe is the fuel pump or the Ignition system. I would change the fuel pump (and filter), and see if that resolves the problem - sure you can test fuel pressure while driving - but it's not that easy to do - and if you don't have access to a fuel pressure tester - getting one is a significant percentage of what it will cost for a new fuel pump.

If you replace the fuel pump, and the problem happens again - try to check for a good spark (while cranking) when the car is stalled.

GOOD LUCK !!!

billschroeder5842

You need to change out your fuel pump.

84s with the L83 engine are notorious for having fuel pressure issues. The factory pump does not have enough umpf to keep up with the demands of the cross fire.

When you swap, put in a 85-89 pump.It has a higher pressure that your L83 will love, as it feeds it consistent, high pressure.

Hot Rod Roy

The fuel pressure in the L83 CFI is a function of the fuel pressure regulator, not the fuel pump. Replacing a good L83 fuel pump with a good L98 fuel pump won't make any difference. This would be a total waste of time and money.

If the L83 pump can't maintain the proper fuel pressure, it makes sense to change the pump, but changing out a good fuel pump doesn't make sense. You won't get higher fuel pressure!

Have you checked the adjustment of your Throttle Position Sensor? It should be set at .53 volts.

Here's a link to some advice from some C3 guys working with similar '82 CFI problems:
https://www.corvetteforum.com/forums...esitation.html

billschroeder5842

HRR, I'll give you 1/2 on that one; the FPR will control things IF there is enough fuel pressure to begin with. The 82-84 pump is a lower volum pump and is known to "fade" as time goes by. The 85-89 fuel pump is a "known swap" on the L83 as the higher pressure will keep the FPR full "charged" at all times.

Now, if the pump is putting out a minimum of 13ish and the car runs poorly then the FPR is suspect. Less than 13ish and you are taking your chances. I had similar symptoms as the OP with my '82 XFire and swapped the fuel pump.... never an issue after.

I'll bet "a dollar to a donuts" (that is one of my grand fathers sayings) that after the OP exhausts his parts inventory and put a fuel pressure gauge on the car, it will come up short and a $40 pump will fix it all.

chagger32

i will try the 85-89 pump and let you know after the weekend how it works out

billschroeder5842

Are you able to test the pressure PRIOR to the swap? Again if you are above 13ish you are good. Hate to throw parts at the car however it is great PM......

Silver85

Would the pump actually turn faster? We are still supplying the same voltage and the number of poles in the motor doesn't change. It would be interesting to see the pump curves of each and compare. I would bet the impeller design between the two is quite different.

High pressure doesn't necessarily mean higher volume but higher volume does usually mean higher current draw.

billschroeder5842

IHBD, it is a very common practice especially is you have ever owned an L83.

http://www.corvetteactioncenter.com/...your-84-a.html (read post #1)

https://www.corvetteforum.com/forums...e-upgrade.html (read post #5)

http://www.c3vr.com/vrforums/c3-fuel...rvette/427017/ (read post #1)

http://www.crossfireinjection.net/faqs.htm (read FAQ #5)

https://www.corvetteforum.com/forums...fuel-pump.html (Read post 4)

There are plenty more out there. I had an 82 with the L83 engine and the C3 guys seem to be way more interested in working-- and have universal success-- with this combo. The L83 was a one-year-only for a C4 so I'm afraid it gets dismissed.

I think concern about premature wear and excessive electrical drawn is unwarranted.

So, OP, its your car so its up to you.

chagger32

I found out it was the alternator today stupid remanufactured alternators.
This weekends project is a brand new distributor and a 85-89 fuel pump I'll keep you updated !
then if all goes well it will be time to start looking into my cluster problems when all gauges light up but yet no numbers on the at the gauges appear well, they do but they are impossible to see.

Hot Rod Roy

I don't have data to back this up, but it seems to me the '85-'89 pump would be loafing along by only having to pump at 13 psi, rather than at 45-60 psi, and therefore consume less current.

It would be nice to see those performance curves that were mentioned!

Silver85

Current draw is directly related to the amount of work the pump is doing. Higher pressure doesn't necessarily mean more work. Increased flow does. So if we flow roughly the same amount of fuel with an impeller designed for higher pressure the current draw will more than likely be very close to the same.

I am sure there is a FLA rating for the pumps. If it fits in in the original circuit I say go for it.

Silver85

They aren't proportional though. An increase in pressure is minimal in its effect on work vs flow.

Buccaneer

Interesting thread... I wonder how it will all pan out?

chagger32

just a update battery is going good now and batee sent me a sample film strip to put over my gauges and it fixed that issue now my battery is at 14.7 hopefully that is normal.
I will be proceeding on doing the fuel pump today and will keep everyone updated after that i will be changing my valve cover gaskets and distributor within the next week!