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L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

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Old 06-10-2003, 04:41 PM   #1
SkipI
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Default Starting problem.. 1989 C4

I am having a problem with my 89 vette. The engine takes anywhere from 5-8 seconds to start when cranking. Here is what I have done... new plugs, wires, fuel pump relay, dist. cap, rotor, and verified good timing. I have not checked fuel pressure because I don't want to spend $50 for a gage to use only once... instead, I jumpered the fuel pump on and cranked after 5 seconds of fuel pump run... no difference. I placed a timing light on the car and verified I had sparks while cranking... the light flashed fine. So, it is not the fuel pump, nor the spark plugs. I could place a test light on an injector to see if they are working? After it starts it purrs like a kitten all the time. It runs strong and without missing or any other problem. HELP!!

Thanks,
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Old 06-10-2003, 04:55 PM   #2
TheCorvetteKid
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Default Re: Starting problem.. 1989 C4 (SkipI)

Skip, I am going through he EXACT same problem with my '89 as well. I've done vitually everything you've done as well as the fuel system pressure test, and I still haven't found the problem.

I am very VERY interested in your progress here - I have a feeling we can use the same solution!

Have you considered the IAC motor?

:lurk:


[Modified by TheCorvetteKid, 10:35 PM 6/10/2003]
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Old 06-10-2003, 05:07 PM   #3
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Default Re: Starting problem.. 1989 C4 (SkipI)

My 88 did this after I installed the MiniRam. The MiniRam doesn't use the 9th injector so I assumed it was because of that. Maybe there's some relavance to your car. Can you verify the 9th injector operation?

KM
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Old 06-10-2003, 05:38 PM   #4
SkipI
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Default Re: Starting problem.. 1989 C4 (88-406)

The IAC motor is new... there is a funny story here... I took it out and left it connected. I turned the key on to see if it moved, but I was in diagnostic mode and the pintle shot across the garage. I decided to replace it after that!! My car does not have the cold start injector. I just replaced the intake manifold gasket and discovered there is no cold start injector. And yes, it was hard to start before I replaced the intake gasket.
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Old 06-10-2003, 05:39 PM   #5
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Default Re: Starting problem.. 1989 C4 (88-406)

The '89-'91 L98s didn't have 9th injectors.

Skip, have you tried a compression test? I thought that was my problem, but my car tested great - 180psi-190psi across all cylinders. It's probably the same in your case, but it's good to rule out low compression.

But I've tried virtually everything to solve this (I've even replaced my injectors!!!) One thing you could try is to test the Coolant Temp Sensor on the front of the intake manifold. I tested mine this weekend, but the numbers looked OK (I saw 2.07Kohms@73degF). Also try disconnecting the MAF sensor and starting the car. If it starts OK, you've found your problem. Have you checked your TPS voltage? The manual says that if it's too high it can cause this condition (I tested THAT too this weekend and I got something like 0.49v with closed throttle; 4.45v at wide open throttle).

I'm thinking about just swapping out my ECM for a spare one that I have just to see if that does the trick. Someone suggested that it may be it.

This is one of those problems that you can ignore for years ('cause the car still runs fines) but it just EATS at you every time you get into the car and start it cold!


[Modified by TheCorvetteKid, 9:50 PM 6/10/2003]
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Old 06-10-2003, 05:54 PM   #6
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Default Re: Starting problem.. 1989 C4 (SkipI)

Thinking about the IAC motor... I disconnected it and started the engine and it made no difference. Just idled at higher RPM after cranking 5-8 seconds.

Skip
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Old 06-10-2003, 05:59 PM   #7
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Default Re: Starting problem.. 1989 C4 (SkipI)

I've never pulled my IAC, and for all I know is probably the original unit. I have a funny feeling that the secret might be with this sensor, but I don't know.

Why do you mention it? What are you thinking?


[Modified by TheCorvetteKid, 9:59 PM 6/10/2003]
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Old 06-10-2003, 06:04 PM   #8
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Default Re: Starting problem.. 1989 C4 (TheCorvetteKid)

I don't think I have a compression problem with only 46,000 miles on the car. The coolant temp sensor was replaced when I replaced the intake manifold gasket (when I work around a sensor, I replace it since they are 14 years old). I adjusted the TPS when I put everything back together. I started the car with the MAF diconnected and got the same thing.

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Old 06-10-2003, 07:21 PM   #9
John Row
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Default Re: Starting problem.. 1989 C4 (SkipI)

I think there was another very similar thread in the past couple of weeks. I don't recall what year, but the problem was an oil pressure bypass. The engine wouldn't start till there was sufficient oil pressure. This bypass held the circuit closed for something like 5 seconds to give the engine a chance to start.
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Old 06-11-2003, 12:34 AM   #10
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Default Re: Starting problem.. 1989 C4 (John Row)

Quote:
I think there was another very similar thread in the past couple of weeks. I don't recall what year, but the problem was an oil pressure bypass. The engine wouldn't start till there was sufficient oil pressure. This bypass held the circuit closed for something like 5 seconds to give the engine a chance to start.
I've read somewhere that there was a batch of bad oil pressure switches that where used in production for 88-89 or so. There were enough of them that they stayed in the spare parts stream for a few years too. I also remember something about being able to tell whether you have one of the suspect units by it's color, but I don't remember what that color was. Anybody out there know anything about this? Pics would help too.
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Old 06-11-2003, 01:35 PM   #11
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Default Re: Starting problem.. 1989 C4 (SkipI)

You spent money to replace (new plugs, wires, fuel pump relay, dist. cap, rotor), without knowing if they needed replacing, but you are too cheap to buy a fuel pressure gauge to tell you if you have a leaky fuel injector? You aren't thinking clearly. A common cause of hard starting is a leaky fuel injector which can be found by putting a fuel pressure gauge on the shrader valve on the fuel rail, turn the ignition on for several seconds to pressurize the rail, turn off the ignition and see how long it takes to lose 1 psi. GM says it must take more than 30 minutes or you have a leaking injector.
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Old 06-11-2003, 01:53 PM   #12
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Default Re: Starting problem.. 1989 C4 (TheCorvetteKid)

Good oil pressure switch is black, bad batches were gray. Saw this at http://www.C4vettes.com - hope it helps. I have the same problem, but now it won't start at all and fuel pump not running unless I charge it through the ALCL. If you figure it out, please share. Thanks.
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Old 06-11-2003, 01:55 PM   #13
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Default Re: Starting problem.. 1989 C4 (jfb)

Hey jfb, while agree with you that a fuel pressure test guage is a useful tool, I bought mine to diagnose the same problem and my fuel system shows to be OK. I would suggest that Skip gets a guage as well, but replacing plugs, wires, pump relay, distributor cap and rotor is just good routine maintenance - you can't fault a guy for that.

Regardless, my car HAD a leaky injector when I first bought it and while the symptom of a hard-start is the same, it only happened when the car was hot. When the car was cold, it started up fine. And this is VERY much in line with what alot of other people on this forum have said. Makes sense when you think about it - when an engine is cold, it likes a slightly richer mix of air/fuel to get started, but when it's hot it creates a flooding condition causing the hard starting problem.

But lets assume that Skip bites the bullet and buys a fuel pressure test guage and finds that his fuel system is OK (as I did) - what do you suggest he ("we" really since we have the same problem) try next?
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Old 06-11-2003, 06:51 PM   #14
SkipI
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Default Re: Starting problem.. 1989 C4 (jfb)

Quote:
You spent money to replace (new plugs, wires, fuel pump relay, dist. cap, rotor), without knowing if they needed replacing, but you are too cheap to buy a fuel pressure gauge to tell you if you have a leaky fuel injector? You aren't thinking clearly. A common cause of hard starting is a leaky fuel injector which can be found by putting a fuel pressure gauge on the shrader valve on the fuel rail, turn the ignition on for several seconds to pressurize the rail, turn off the ignition and see how long it takes to lose 1 psi. GM says it must take more than 30 minutes or you have a leaking injector.
Okay, here is how I justified not getting the gage. I replaced the plugs, wires, cap & rotor due to age. When I replaced the plugs, there were no plugs with gas on them or the smell of gas.... I would think this would eliminate leaking injector. Regardless, when I jumped the fuel pump on via the ALDL for 5 seconds before starting the car, it still took excessive cranking. I would think this would eliminate low fuel pressure on the rails via leaking injector or bleeding back through the fuel pump? It is not so much that I am cheap... just that I figured I could eliminate the need for a gage by doing other tests.

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Old 06-11-2003, 06:54 PM   #15
SkipI
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Default Re: Starting problem.. 1989 C4 (SkipI)

Update.... today after work when I got into the car, I barely had to touch the key for the engine to fire. It had not started this fast in some time! When I got home I turned the engine off and when I restarted it... yep, you guessed it, it took excessive cranking!! :crazy: You just got to love this!! Anyways, the problem is random and not each time. I throw this in to add confusion to the troubleshooting!!

I do appreciate all the replies guys!! :thumbs:

Thanks,
Skip


[Modified by SkipI, 10:55 PM 6/11/2003]


[Modified by SkipI, 10:55 PM 6/11/2003]
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Old 06-11-2003, 07:01 PM   #16
SkipI
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Default Re: Starting problem.. 1989 C4 (SkipI)

Hey... what about this.... this was on a corvette service bulletin...

Component: FUEL:FUEL INJECTION SYSTEM
Summary: INTERMITTENT NO START, LONG CRANK, STALL, OR ENGINE SURGE-BOTH MAF RELAYS(BURN O FF AND BURN OFF CONTROL)SHOULD BE REPLACED-1988/89 CORVETTE DG

Anyone replace these relays to fix this??

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Old 06-11-2003, 07:17 PM   #17
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Default Re: Starting problem.. 1989 C4 (SkipI)

I've heard of people replacing the two MAF relays but I don't know if it helped at all. I never considered them because I know that my burn-off relay works cause I can hear it buzz for a second after I drive the car.

But it's worth a shot seeing as they aren't much money.
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Old 06-11-2003, 07:38 PM   #18
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Default Re: Starting problem.. 1989 C4 (SkipI)

I've been following this thread, and others like it, since I have the same problem with my 89 coupe. Before rebuild it started quickly, cold or hot. After rebuild, cold takes 10 seconds or more of cranking before it fires, 5 seconds or more when hot. I built it up stock except I added headers, Bosch 21# injectors, eliminated AIR and EGR. All sensors are new, IAC is new, fuel pressure is 42# with new AFPR but it drops significantly in an hour. Once, as a test, I removed plenum and fuel runners then I loosened and lifted the fuel rails with injectors intact but left the fuel lines connected. I turned on ignition to charge the fuel rails and looked for injector leaks... all 8 remained dry. So... no leaky fuel injectors. Timing is 6 degrees before TDC, as per sticker in engine compartment. Once cranked it idles and runs fine except it has an intermitten skip at idle that seems like an ignition problem. Acceleration is strong. Fuel milage is 3 to 5 MPG less than before rebuild. I'd sure like to find what's causing this hard cranking condition.
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Old 06-11-2003, 07:58 PM   #19
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Default Re: Starting problem.. 1989 C4 (Frodo)

Frodo, have you considered the two MAF relays?

It sounds to me like you've tried virtually everything else. Like I said above, for the cost and effort it's worth a try.
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Old 06-11-2003, 11:55 PM   #20
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Default Re: Starting problem.. 1989 C4 (SkipI)

Wet plugs don't always show up with a leaking injector. When the air/fuel is way too rich, the engine won't start easily. Also, your problem is intermittent and looking ONCE doesn't prove you don't have a leaky injector. And, a leaky injector also doesn't necessarily lower the fuel pressure, so your test by turning on the fuel pump for 5 seconds isn't conclusive. Spend the money and prove beyond the shadow of doubt by actual fuel pressure measurement that your injectors are or are not leaking.
Check your initial spark timing, and check each spark plug wire with your timing light to prove that each plug is firing. A vacuum leak will make it hard to start. Measure your manifold vacuum, look for vacuum leaks on ALL of your vacuum lines. Do you have any stored error codes? Check them. What is your TPS (throttle position sensor ) voltage? A stuck EGR valve can cause too low air/fuel ratio during cranking and hard starting. A defective MAF sensor can cause hard starting, try disconnecting it and attempt a start. Put a low power 12v lamp across each injector socket and observe that each is being pulsed when you crank the engine. Let us know what you find.
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