need some help....starting issues

[WestTexasVette]

Hello all….I own a 1996 LT1 with 38k and no mods. I have been having intermittent starting issues and was hoping to get a little input from you guys. My car will start just fine in the morning 90% of the time. Car runs perfectly…. Turn car off to run quick errand or whatever car will start fine. However when I let the temp come down to 115-140 and attempt to start, it takes a few times to get started. It will start, sputter for 1-2 sec at low rpm then run just fine. I have replaced the fuel filter and just today replaced the fuel pump. Have not had a chance to test adequately but still don’t think it fixed the problem. I thought is might be an injector leaking, but the problem is not consistent. Could the IAC be the culprit? Perhaps the fuel pressure regulator? Also, when it does act up, I hear a whining noise from the engine area. Any advice? I have posted this issue before. Received good advice last time which led me to change fuel pump…

Thanks

 

[Tom_Bacon]

sounds like the same problem again. I understand that the OEM is very sensitive to voltage drop. A 4 volt drop will effect fuel delivery pressure, so you might also check your electrical system.

 

[Skant]

Perhaps these symptoms come and go with the weather? If the problem was 'fixed' before, but came back recently... maybe it's a hot day issue as the weather heats up. A vapor lock kind of problem?

- Skant

 

[Chick]

This is what I would do:

I would first monitor the 'fuel pressure' when this occurs. I'd set it up with a 'fuel pressure gauge' on it and duplicate the condition. We could find that the pressure looks lower than normal. If the car loses 10 or 15lbs while cranking it won't start or it will take time to get it running.

The problem then, most likely will be the 'fuel pump module'

I suspect this could be your problem.
------------------------
If this shows normal then I would check it with a 'scan tool' while cranking it... another possibility is the 'distributor' (Opti) There is a 2 wire connector that plugs into the side of the distributor that controls A and B circuits. I have also seen corrosion in this connector. They can cause a starting problem.

Un plug the connector and take a visual. See if there is any corrosion. If there is. the distributor and the wiring harness will have to be replaced.

Generally for this there will also be a code in the history which may or may NOT trigger the engine check light.

 

[WestTexasVette]

Thanks

Thanks for all of your input….

I’m starting to see a pattern with this issue. Only occurs when car is driven and sits for 1-3 hours. Sits 8 hours or so it will start fine. Is it at all possible related to pressure regulator of IAC?

Thanks again

 

[Ric]

Based on my experience with my 88 Vette, you have one or more leaky fuel injectors. I went through the same problem. After not having driven the car in several days, it starts instantly. After driving any distance and leaving it for "enough time", it was very slow, hard to start. However, IF if left it overnight, it would start instantly again. The problem in my case was that two injectors were leaking such that after shutting the engine down after a drive, and leaving it, fuel would enter the engine and cause a flooding type of reaction. However. left along long enough, this gas evaporates and there is no longer the flooding problem. New injectors solved my problem.

...Ric in Vegas

 

[WestTexasVette]

Thank you

Thanks, Ric and all

What other symptoms were you having before you replaced the 2 injectors, and how did you pinpoint the leakage? I am not experiencing any other issues…just hard to start sometimes after being driven and left for “enough time.” Also, I’ve been told that I would be able to smell gas from the engine if injectors were leaking. Before I replace, I am going to get a pressure gauge and run some tests. Where should the fuel pressure be when left overnight….where should it hold steady? Thank for the help

 

[Ric]

Fuel pressure should stay at about 42-45 psi or so over night. If it drops noticeably, especially say within 20 minutes or so, it means that fuel is going somewhere. Most likely, into your engine via a leaky injector and flooding it. You may notice, when this happens, a bit of smoke out the tailpipe when it finally does start.

I tried to investigate everything before finally having a shop replace the injectors. But, it solved the starting problem. I ended up with a new problem that no one on earth knows what to do about, but it did fix the start problem.

So, the first thing to do is put a pressure gage on the value near the fuel rail and read this with the ignition on, motor not running. If you then turn the ignition off and monitor the gage for a while, it should stay put pretty much with only minimal change over the next 12 hours or so. If it decreases, then, other than the injectors being leaky, it could be a defective diaphragm in the fuel pressure regulator allowing gas to be sucked by in the vacuum line into the engine. Or, fuel is flowing back into the tank. My bet, based on your symptoms, however, is the injector issue.

The problem is that if you have a shop do the replacement, it costs a lot since there is significant labor involved in getting at the fuel rail so you can take the old ones out and put the new ones in. It is about 6 hours of labor! Also, if you do this, it seems that you want to have a matched set of injectors put in at the same time, don't just replace the defector ones. The matched set is supposed to make sure that the fuel delivery is the same, within some tolerance, for all of the injectors. So, some are injecting more fuel than others as the engine runs.

...Ric

 

[RedRagTop]

Mine does this on occasion as well and Ric's theory makes sense. I don't smell gas either but the times match. I have to long crank or give it throttle sometimes to start. What is the problem no one on earth can help you with? If it's corvette related I bet some folks here would beg to differ!

 

[Ric]

RJSRocket

I never posted a followup to my problem, so here goes. As I mentioned, I ultimately had the injectors replaced. This appeared to absolutely fix the hard start problem...but, now the engine ran noticeably rough! Diagnostics indicated that something funny was happening with cylinder #4 based on watching the waveform of the vacuum line, after synchronizing with the number 1 cylinder. So, the professional thoughts, from the shop, included the idea that it might be a valve issue, even, maybe, wear on the cam such that that particular valve was not being lifted quite sufficiently. Why this would now appear, however, and was not evident before, seemed strange to me. After being a worry wart with the mechanic, the shop finally agreed to pay for a second opinion at the local Chevy dealer. Actually, I believe that my guy was far sharper than the tech at the dealer...but, anyways, the dealer tech reported that he thought the injectors were bad! Of course, they had just been replaced! When my mechanic went to pick it up at the dealer, it would hardly run now! Very strange. Back in the shop, it wouldn't even start now. So, back to removing all the hardware to get at the injectors. What was found, in this case, was that the injector for cylinder #5 was stuck OPEN and shooting out gas like crazy. We don't know what happened from the time the car entered the dealer to when it came out but when it went in, it was starting fine but just running rough with a hint that maybe something might be wrong with cylinder 4.

This time, we replaced all of the injectors with GM AC/Delco parts, actually made by Bosh. Now the engine runs great, absolutely no hard start issue anymore, and it has lots of power!

I am not sure that there is much that can be learned from this experience that is transferable to another Corvette but it sure was a long drawn out affair and could have just been bad luck.

Can you fix my left window? This past weekend it quit working! Ha. What a car.

...Ric

 

[RedRagTop]

Fun fun eh? Looks like this injector thing may be a fairly common prob, surprised you needed it at 38K though. I bought mine with about 65K and hoped most of the early bugs had been fixed already, and I think most have. I have 2 recall stickers on my fan shroud but they are so faded I couldn't get the numbers off them. Sure as hell hope they were for the bad right rear a-arm that tended to fall off and the rim welds that tended to let go!
I usually don't have to do a lot of warm starts due to this car being mainly a weekend cruiser for trips so I think I can live with the occasional long crank start. Funny, I only noticed this problem after changing the wires, cap, rotor.
As for the window on one side only failure I would suspect switch or wiring to the door probs, does the power mirror still work on that side, locks?
Good luck!:t

 

[TerryD]

I went from the hard start condition you spoke of, to no start. Replace fuel pump, ran ok for a few miles then died again. This time I couldn't re-start engine. Replaced opti, thinking that was it but after getting it together still no start. Finally turned out to be a bad coil. Might want to check that...part is cheap, replacement is easy

 

[TerryD]

I went from the hard start condition you spoke of, to no start. Replace fuel pump, ran ok for a few miles then died again. This time I couldn't re-start engine. Replaced opti, thinking that was it but after getting it together still no start. Finally turned out to be a bad coil. Might want to check that...part is cheap, replacement is easy

I had my wires, plugs, and fuel filter replaced a few months earlier, f

 

[Ric]

The injector issue I have been describing is on an engine with 61,000 miles on it, not 38,000 or so. The window is not a switch issue since I hear it run. It just doesn't move the window up or down. I think it is in the window transmission.

...Ric