89' Black coupe / L98
Pulled motor out 2 years ago, stripped down, block dipped,punched out .030, new pistons and rings, crank balanced and polished, compu-cam 2032, trickflow heads, full length headers, punched out cats, flowmaster exhaust, adjustable fuel pressure reg. (set at 48psi), 58mm throttle body, tpis stage V chip, new injectors, possibly a couple other small mods I can't remember, but thats most of them.
Removed motor, did all of the above and now I have hard start-ups, only after the car has set for a period of time minimum 6 hours or over night. I used to have to crank the motor about 10+ times before it would start and run. Repalced all the temp. sensors including the one in the front of the intake manifold, but nothing has fixed. Only thing that works for now was removing the harness off the temp. sensor in the front of the intake manifold (which I replaced twice) and closing the loop with a paperclip, i for now ran two wires into the car with a toggle switch to make easier for now. You hit switch or place paperclip and the motor starts instantly, but w/o especially when cold and I'll be cranking for ever.
Any Ideas as to what's wrong or what may need to be adjusted, Please Help
Thanks in advance to all of those whom reply here or to my email fredjr@nycap.rr.com
Looking forward to your help. THANKS FRED!!!

 

Your paper clip makes the ECM turn on the start injector because it thinks its winter. It sounds like your TPS voltage is too low or the ECM isn't going through the start proceedure correctly and the start mixture is too lean.

 

I had a hard starting (excessive cranking when setting for 8hrs. or longer )problem with my wife's 85 a couple of years ago. LONG story short, I replaced the fuel pump (after a LONG list of other things) and the problem went away. The weird thing was that all the fuel pressure/bleed off tests I did in the beginning showed that the pump was NOT the problem.

 

What is the proper voltage at the TPS????
Thanks
FRED

 

Actually shorting the pins on the ECM temp sensor lead should make the ECM think the engine is very hot! Should set code 14, does it?

Are you using the stock ECM? Do you have access to a scanner to see what temp the ECM thinks it is? Could also put the car in limp-home mode, which bypasses the chip.

I would start with going back to a stock chip in the ecm and see what that does.

BTW, 89 does not have a cold start valve. First year w/o. You sure that chip is for an 89? Also do you think the 59mm is a little large for your engine? Could be making you lean, especially before the ecm has learned the steps for the IAC.


[Modified by PeteL, 9:05 PM 5/28/2002]

 

The chip in the ecm was a special burn stage V chip from TPIS specifically for my vette. Yes, the 58mm is rather large, bought it when I thought bigger was better. Just for note the car started fine when I first installed the 58mm throttle body, it was after the engine removal and mods when the hard cold start-ups started. I also plan on changing the intake and runners thought the 58mm would go well with one of the aftermarket intake and runner packages.
Any ideas as to which one is good??? TPIS mini-ram or Lingenfelter package or any other suggestions??? One of the last things I can change on the motor to get a few more ponies out of her.
Thanks Again
FRED

 

the 58mm TB wouldnt really be any better even with the SR or MR, 52mm is adequate for those two, now if you used some forced induction or had a big block in there it might be a different story

I think SuperRam (Lingenfelter) is better, some think MiniRam is better. I personally believe both are good but that the MR is best for the 6 speed and the SR for the automatic. Either would be good for the 4+3.

Proper voltage for the TPS is .57 Vdc

As for the hard starting, its a fuel problem, how old is the filter and pump? What type of injectors did you put in? If none of these turn out to be the problem, it has to be the computer and the chip.

 

The filter is only about a year old and I tried replacing the fuel pump, that didn't help either. Injectors I replaced with the motor rebuild - stock 19psi injectors from TPIS, the only ones that I found that would fit w/o having to modify the fuel rail posts.......
Thanks for the voltage number, I will check.

 

Sounds to me like the fuel pump is not bringing up the pressure to the rails until the oil pressure switch is kicking in. First think I would check is fuel pressure at cold start-up. Fuel pump should run for about 2 secs when key is first turned on, if not check fuel pump relay for function. But I would start with fuel pressure at cold start then go from there.

 

I checked that also, the second you turn the key to the run position the fuel pressure guage registers 45 psi, but I'll have to check again when the motor is cold, but the fuel pressure is there. Do I maybe need an after market pump????

 

Naw, stock pump will do fine.

Think 45 is too high, although you say you have 19# injectors. Stock injectors for the 89 are 22#'s at about 40 psi. If the chip is programmed properly, this should be OK.

Only thing that makes sense is that cold needs more fuel than warm, therefore engine is not getting enrichment when cold. If you short the coolant sensor and make the ecm think you are very hot, it starts. I have to think that that chip is for an 88 or earlier car and not an 89 that does not have a cold start injector.

You never answered if you get a code when shorting that temp sensor?

Pete

 

You know, maybe they were 22# injectors. I replaced with stock # from TPIS. The answer is yes, at least I think so. When I get in the car in the AM, I press thte toggle switch to close the loop and start the car. If I don't return the switch back to the run position immediately the check engine light comes on. I assume that is for code 14, but when I turn the switch off the light goes out.

 

Have you measured voltage at the temp sensor and the TPS? Should have a 5V source. Orginal 89 ECMs had a problem, but you should not jump to the conclusion that it's bad, but it could be. I would try the orginal chip first and see what it does. I would also measure voltage at the TPS and temp sensor. If you can, get the number off your ecm.

Pete

 

No, not yet. Voltage at the temp. sensor? , the harness? that plugs into the sensor? if so, which side or does it not matter??? Key in the run position or off? Let me know and I'll go and pull the cat into the garage to ck....
Thanks FRED

 

yellow wire on connector to coolant temp sensor (below throttle body, front of engine) is 5V and black wire is ground. Key needs to be on to read the 5V.

On TPS, Gray wire (term C) should be 5V and Black wire (term A) should be ground with key on.

Engine does not need to be running, just key to on position. Also you can try an alternate ground to the black wires by using say the battery negative cable for comparison.

 

Thanks for the info, getting kind of late, I'll ck those #'s tomorrow and get back to you. Thanks Again
FRED

 

Agree

 

I checked the voltage at the coolant temp sensor, you said 5V, I get a reading of 3.91. Is that good / bad or what????
FRED

 

PeteL, are you on the forum this evening, the voltage at the coolant temp sensor was 3.91, is that too low and causing my hard start-ups????????????? Thanks FRED

 

That's off by 20%, but doubt it would cause a no start. Hmmm. Same at TPS?

My next step would be to drop the ecm (get the number) and swap back to the stock chip just to see what happens.

I have to re-read this thread to catch back up and sleep on it!

Pete

[edit] re-read and I think maybe you were too rich at cold start? Does it smell of gas at all if you crank with the sensor hooked up and engine cold?

There was also an error in some 89 chips that screwed up cold start, you would think that TPIS would have the right code, but you never know.

Also a scanner would be a very nice thing to have right now. I know in the tuning section there are links to free software and an inexpensive cable, you should do this if you have access to a laptop or pc you can get near the car.

You can check the temp sensor with your ohm meter. It should be around 3,400 ohms at 70*F. This worth a quick check.

I'll sleep on this a little.


[Modified by PeteL, 10:08 PM 6/6/2002]