I changed from carb to tpi. The unit is off an 86 Camaro. I used a Painless Wiring harness. Put in new sensors. The car starts and runs for only a few seconds, and shuts off. With the accelorator opened somewhat I can keep the car running - rough with some back firings through the exhaust. I replaced the fuel pressure regulator between the fuel rails, and have a constant pressure of 40 -42 pounds. I connected the Painless Wiring "ignition wire" - pink and black - to the battery wire of the HEI. A volt meter shows the power drops from 12 volts to any where between 8 - 9 volts when in the start mode, and running. When the engine dies, it goes back to 12 volts. I have set the TPS at .54 volts.
It seems that the engine needs the extra air (opened accelorator) to run, but still hardly runs. Is it running too rich, from the low voltage going to the distributor, and not getting a hot enough spark to burn the fuel? Is opening the accelorator and allowing more air, leaning out the mixture to where it can run? I assume that the back fires indicate the timing is less than wonderful. I am using the OE computer that came with the unit. My engine is a 360 sbc, with a mid range cam, headers. I have ordered an adjustable pressure regulator so I can get more fuel pressure. The injectors are new and for a 350. I have also ordered a high amperage alternator. I have adjusted out the throttle blades of the throttle body. Any thoughts are deeply appreciated.

 

My first question would be, why is there low voltage to the distributor? This may not be applicable since I don't know the year of your Vette, but if its say pre-74, and had a points style distributor originally, then the power wire going to the distributor is a resistance wire. This is a common issue when swapping to an HEI. Run 12 volts to the distributor, and hopefully your problem will be solved.

 

OK, you had a points dizzy on the old carb setup that black wire with it's mate covered in cloth is a bad news bear for you, you need to into the harness at the terminal in the bulkhead behind the fuse block, and you will see if you pull the fuse box off that the wiring code changes to PINK, that is the circuit you need pull the HEI power off ...directly, that black wire is a resistor wire to limit coil current, and will mess up a HEI like mad....

i'ts mate running to the starter terminal, the outboard one...I forget how it's marked...P I think for points...the other one is S, I think for the starter energize off the ign switch....purple wire circuit....

the pink wire should obviously remain at 12/start/bat voltage all the time.....14 with a good alt....

 

Sorry, its a 77 vette. The distributor is the HEI that came with the unit. The computer ignition wire that I have connected to the battery hot wire at the HEI, is wrong. I'll take it back into the car, and try to find a hot connection there for run and start. This is probably why the voltage at the distributor is so low. I'll move the wire and hope for the best. Thanks so much for your imput! kip

 

PM me for more direct help, IF I fail to spot this thread....

 

might help to scan the ALDL to see what the ECM is telling you.

 

sounds like your idle air motor is bad or needs cleaning. i have a tpi on my 67 camaro. if the car runs ok with the throttle and won't idle that is where i would start. you can pull it off and clean it most of the time. locate on the throttle plate. this little motor helps it idle. also, i would check with someone like tpis to burn yoou a custom cpu. they did mine for my 327 and it runs great. also, make sure you have the switch wired up that lets the ecm know your in neatral or park if your running an auto. there is also a switch for idling it up for using an a/c

 

these old tuneport ecm have a large range before setting off any check engine lights. my painless wireing harness came with a check engine light, it has never gone off. if you have some type of scanner you maybe able to find out something.

 

If your problem is JUSTat idle, you may nrrd to adjust the throttle plate opening in the throttle body. This should be cracked just slightly. This adjusyment is accomplished by means of a small threaded screw on the left side of the throttle body which acts as a stop for the throttlr arm. Many stock throttle bodies have mrtal plugs over this adjustment to conceal it and prevent users from messsing with this adjustment.

 

Sorry for the delay in replying, this is my office computor...

Is the iac motor a problem to get out? I have read somewhere else where these clog up and get ugly... maybe this is part of the issue. I have gotten the timing where the car did almost run, so I am guessing its at least close. Can't set the timing of course, until the computor closes the loop...

Is it necessary to disconnect the negative battery terminal to let the computer reset, every time I try something else? Like taking out the iac motor...? thanks so much... I know this just should not be this hard. thanks - kip

 

I did just think of one other thing. I am using a wiring harness from painless. I do not have a cold start switch connected in the system. Here's why. I do not have a place for it on the front "edge" of the intake manifold, as most pictures show. There is only a place for the coolant temp and water inlet. Where does the cold start switch go, if not on the front of the intake? And this may be too obviously stupid a question, but is this possibly one of the reasons this will not start. I will attempt to remove the iac motor this afternoon, and inspect its condition. Again, much thanks... kip

 

I would suggest definitely getting either a manual for a TPI car, or one of the popular books like "TPI Swapper's Guide" to get a real thorough understanding of how everything works, along with an affordable scan tool. It sometimes takes a while to sort these systems out, but once you do, you'll be very happy with the performance. Good grounds are very important, along with a good charging system. Keep in mind that when you adjust the throttle blades, you may have to go back and readjust the TPS. Good luck !

 

Have you done anything about VATS? If not, this could be the problem.

 

I have had one of the books on swapping the tpi onto a carb'd car. There is a lot of stuff that is not in the book, that I have found on different web sites. There is no vats stuff on the car. The directions from painless simply said to ignor this.

I did remove the iac motor and clean it today. It was carboned up. Found top dead center by watching the valve lifters, and noticed I was one tooth off on the distributor placement. I corrected this, and still the car will only start with the throttle opened with the accelorator pedal, and then, it races at high rpms and then drops down, and will stall if the accelorator is not activated again. So, what does having so much more air have to do with why it will not idle? Does the opened throttle have something to do with the computer readings, or is it more of a mechanical thing? I do not have a scanner for this. Is that something that can be purchased at a regular auto parts store? thanks - kip

 

In reading another web site, someone wrote to make sure that there is no air leaks between the maf sensor and the throttle body. I'm sure that my set up could certanily allow for this leakage. Is part of the issue? How does opening the accelorator effect this? thanks

 

Yes - you must not allow any "un-metered" air to enter the engine. All air processed by the engine must be metered by the MAF sensor. If air is "leaking" in elsewhere you will get a lean condition.

If the leak is constant regardless of throttle pos then opening the throttle could lower the error percentage to a point where the engine will run acceptably. If the "leak" is large, it's possible that at idle the engine is taking in more un-metered air than metered, which would lead to severe idle issues.

There are freeware scanning software packages available for TPI setups - you just need a cable. Google AKM Cables

 

Do you have an oil pressure sensor and 02 on the car?

You say you have between 40-42 psi on the rail. Are you using a in tank fuel pump?

I assume you wired the the timing advance wire to the HEI?

Are you sure the TPS is at .540? Should be at .525. But .540 may still work.

If you check at the hose going to the MAP are you getting about 20 psi constant? Can you get it to run long enough to check this?

Jim

 

Thanks for the input. I assume that "Freeware Scanning Software" is something available over the internet? and I would use my lap top? Or is this a scanning tool like they use at Auto Zone, when the check engine light is on? It has an in-line pump, with the return line to the tank. I'll drop the tps to .525 and see what that does. As far as the "timing advance wire" - I'm not real sure exactly what that is. There is the "ignition" wire, in the Painless Harness... but that's not what you're referring to. And of course the HEI, also has the four wire connector, that connects to the wiring harness... but I'm not sure this is what you mean. I assume that the four wire connector is what controls the HEI from the computor.
The leak in the air intake, is due to the fact that I could not use the original rubber connector between the throttle body, and the MAF sensor. Soooo, I rigged up something, that would allow me to make an immediate 45% bend at the throttle body, and then used a 3" metal flexible tubing (like might be used for your clothes dryer venting) to bend around another 45%, thus allowing the MAF and air filter to lie over the driver's valve cover. Where this metal tube connects at one location, I simply have it bend inward, so to fit inside the other piece, and this is where it could be pulling in large amounts of air. I'll either think of some other way, or fill the connection with gasket maker, to see if this is the issue. I hope it is.

I should also mention that there are several items not connected to the computer. They are: the vss, the egr valve, the park/nutruel switch, the cold start switch and the knock sensor. In my reading of the Painless instructions, it appeared that these did not need to be connected, for the car to opperate. Granted, it may well run better with them... but some seemed to deal only with exhaust and such. My concern was over the cold start switch, so I tried to locate one yesterday, and failed terribly. Even the GM dealer could not get me one, and if he could it'd been about $120.00 Again, thanks so much.

 

Well, I fixed the air leak situation. The car still has the same issues. Barely starts, working the throttle allows it to start, then the rpms jump up probably to 2000 -3000, and when you stop working the throttle, it dies down, and quits. Help - kip