What causes this?

- The car starts immediately when it's cold
- When it's hot and cranking, the voltage drops on the meter
- When driving around the voltage reads around 13.0 volts but drops to almost 11 when cranking
- Sometimes i will need to crank it, back off, and crank it again to fire, or just crank for a very long time

 

Your voltage SHOULD drop to 11 or less when cranking, that is when it gets hit the hardest. Keep in mind the alternator isn't turning enough to charge it at that point.

It sounds like leaky fuel injectors have hit you.

 

If it bogs and bogs when youre starting it hot, that would sound like alternator failure, and its sucking power off the battery while the car is running.

If its not doing that, and just wont fire, then it may be injector failure. Youll need to hook up a fuel pressure gauge at the rail, and shut the car off. If pressure does not hold, 1 or more is bad. And you can send them to Rich @ CruzinPerformance for cleaning, or just buy all new ones.

 

Seems like this topic has cropped up alot lately, have you done a search on the forum?

 

Huh?

 

thanks vader, i just did a search
i did not realize this was such a common problem

yes the fuel smell is there afterwards so it's probably getting flooded

2 more questions:

1. How expensive are these to rebuild or replace?
2. Other than flooding the engine, is this doing any damage? My hobby car funds are a little low so i will probably hold out until a see a good set for sale on the forum.

 

I had this problem.

My alternator was dying slowly, and everytime I cranked her when hot, it sounded like it was bogging and wouldnt fire. In other words, it cranked and cranked, very slowly and wouldnt fire.

 

That sounds more like your battery was dead from the alternator not charging it during your drive.

 

Both needed replacement eventually, but the alternator was at fault.

Replacing the alternator fixed the problem and it cranked fine from then on.

That battery died at an autocross.

 

looks like i have some diagnosis to do
is there any way i can check the voltage regulator on the alternator?

 

I cant think of the way to test it, but if you run a search youll probably find a post by jfb on how to do it.

I would suspect the regulator if voltage was wildly varying at cruise, not if it was steady.

 

seems like it varies quite a bit... from about 12.8 to 13.8 or so
I think you are right about the injector leak, but I also think the voltage regulator may be on the way out

 

Seems that a lot of replies kinda vary off the original question....
From prior experience with other GM products.....check your coolant temp sensor to the ECM. If it has failed, then it could be telling the ECM that your engine is cold all the time, even when it is not. This causes your ECM to tell your cold start injector to provide additional fuel when cranking, which in turn floods the engine which causes the hard start when warm, but works just fine when cold. I tend to think this especially due to the fact that you smell fuel during this time.
See if you can find the leads for the cold start injector and disconnect it prior to starting when warm. If it starts as normal, then there is your problem!

Sorry I have no idea where the cold start injector is located, or actually, even if there is one on the Vette....Im still kinda new to all this..been working around those 2.8 liter engines way too long!

But, if it is there...this is just another item to check out before yanking all those injectors.

RDW

 

The cold start injector is on the driver's side, bolted to the intake manifold between the two pairs of runners.

Worth checking out, IMHO.

Jake

 

Very true.


True, but not completely correct. Yes, it could be excess fuel due to the cold start injector operating when it shouldn't, but the cold start injetor really has nothing to do with the ECM on a Vette. The 85 - 88 Vettes had a cold start injector also known as the cold start valve (CSV). This was eliminated on 89 and later Vettes. The Vette CSV is directly connected to a cold start switch (CSS) which is located under the throttle body in the front of the engine. The CSS is a thermo time switch meaning it sends a signal to the CSV based upon its current temperature for a limited time. At cold temps and cold engine startup the CSS activates the CSV to enrich the fuel mixture for starting the engine. If the CSS is bad it will activate the CSV unnecessarily during warm start causing flooding and a gas smell. The CSV has no electrical connection to the ECM in the Vette.


True. However, if you disconnect the CSS and that doesen't solve the problem, you cannot rule out that the CSV injector isn't leaking on its own. Even without a malfunctioning CSS, the CSV could be partially stuck open. Not real likely, but possible. Or it could be one or more of the other 8 injectors. If it is a CSS problem, the switches were available from GM last year when I checked and weren't too expensive. If it's the CSV you will need to get it rebuilt, as there are no new ones available from GM or aftermarket sources. The 85-88 CSV is a special shape injector not interchangeable with the other 8 injectors.

Try starting the car when warm with your foot all the way to the floor on the accelerator. That puts the ECM into "clear flood mode' and it cuts back on the amount of fuel it lets the 8 main injectors spray. If it fires up quickly, you probably have a leaking injector or injectors.




[Modified by Mike_88Z51, 10:19 PM 6/28/2004]

 

Mike,

Thanks for the "enriching" lesson. Im sure it will help with the troubleshooting.

Rob

 

WAMRTexas92C4, thank you for the compliment. Having experienced the same type of problem with my 88, I learned a lot about the early C4 ignition sequence from the Helms manual and the excellent members of Corvette Forum whom I've been able to lean on in time of need. Their rich knowledge of the C4 is unsurpassed.

Bilyk, Although I believe that the problem is due to leaking injector(s), it is a good idea to check the alternator too. These cars are very dependent on the correct level of electrical power to run properly. Trouble in the alternator area could make things worse. Most Autozone and Kragen/Checker stores will perform a free alternator/starter/battery check for you. A quick test is probably a good idea.


The reason I tend to rule out an electrical problem in your case comes from your own post. This indicates to me that it is a hot start fuel mixture problem. I would expect an electrical supply issue would impact cold starts too. Perhaps not as much, but to some extent at least. The difference in fuel mixture requirements is the one big variable in cold start / hot start problems. If it starts easily in clear flood mode then it is almost certainly an injector or fuel delivery problem.

 

Months ago I posted "88 hard start when warm". I received many suggstions most being leaking injectors. I tried the other less expensive ones first. I have changed 3 burn off relays, the thermostat and the cold start switch. I was advised by Rich at Cruzin Performance to test the cold start valve(injector) before sending it for remanfacture. This is performed by removing the injector while leaving the attached feed line connected and pressurizing the system. This is the test to determine if the injector is leaking. Mine did not leak. I have also pressurized the fuel system to find if the pressure drops back to the fuel tank or forward to the injectors. It dropped quickly forward and only when the engine was hot. I now feel the only option left is to change the injectors. Does anyone have any suggestions or experience which replacement injectors would be best, keeping in mind that cost is an important factor. Some forum members have claimed to have had improved performance by using Ford Motorsport 24# injectors, and they are more reasonably priced. Hope my experience provides some help. I still have the same problem.

Frustrated,
Rich

 

Here's some more food for thought, and I don't even know if it makes any sense. My '88 had the dreaded "hard to start when warm" condition and common wisdom said it was leaking injectors. I put my fuel pressure gauge on and tested everything and though there was a drop in pressure it wasn't real significant. I developed a leak in my intake manifold and decided to replace it myself. While I had everything apart I figured it was a great time to send my injectors to Rich at Cruzin performance. His tests showed they were dirty but not leaking. After cleaning I reinstalled them with my new intake gaskets and the car started great...for about a year. My hard start was back. I started noticing some oil on the ground under the rear of the engine. When I put my hand behind the distributor I discovered the rear intake sealant was leaking. Bummer, time for another intake gasket job. This time, I didn't send the injectors out. In fact, I never took them off the intake. I just replaced the gaskets, used "the right stuff" on the ends, and buttoned her back up. I haven't had a leak or the hard start problem since. It's been about 7 months now without any problems, well not with hard starting at least!

Does this make any sense?

Ron