Tri458

Hi, my 305 starts okay but will idle for about 10 minutes then cuts out and will not restart.

Any ideas please?

Tuned Performance

iTrader: (92)

Make right turns ! you should install a fuel pressure gauge to see if you are loosing pressure and have cavitation. If could be a wiring issue as a Ursula of wiring harness age and exposure to heat. most issues with the tpi harness is from po splicing and poor repairs or in the distributor area due to age and heat

Tri458

It's a transplant motor in my 58 apache... Using the original ECM and harness, but using only the basics to run. It has an in- line fuel pressure regulator and it's showing a constant 40 psi. the EGR is disconnected, as is the VSS, air switch (divert solenoid) and canister purge control.

It's only the 4 th or 5 th time I've had her running, and both times she has run long enough to get up to temperature she has stumbled and cut out. If I leave it a while she starts 1st turn of the key but straight after she will not fire stall...

Tuned Performance

iTrader: (92)

Sounds like its heat related. When it dies do you have spark, injector puse, good fuel pressure or too much ?

Tri458

I will check everything on Wednesday and let you know. It's midnight here and I have work tomorrow. Fuel pressure is fine.. 40 psi, but have not checked the spark etc yet. Thank you.

ASE doc

Heat related failure of the ignition control module(inside distributor) is common on the GM HEI distributors. If no spark when the engine dies and you try to restart it, replace the ICM. Don't bother having it tested at the parts store. Since this is a heat related failure, the unit will probably test just fine on the bench.

There is also a pick up coil mounted inside the distributor, just above the ICM. This small coil produces a pulse as the distributor shaft turns. This pulse is used by the ICM for ignition reference and sent on to the ECM as a crankshaft position reference. This coil can also suffer heat related failure, though not as common as ICM failure. You can test this coil for resistance. It should read between 800-1200 ohms at room temperature.

Tri458

Sounds like good advice, thank you. If it's not raining here tomorrow, will check through the list... Hopefully I will pinpoint the problem.. Will let you know. Thank you

fox_305

I had a similar issue on my 91 tpi, I turned out to be a bad fuel injector so you might want to check them. It only happened when the car was hot and then it would not restart tell the motor got cold, 15min or so.

Tri458

Yes, I have an 89 Vette TPI in my 54 chevy and it cut out on me. Turned out to be a shot injector. Unplugged it and got home on 7 cylinders.

Didn't know they were affected by heat.. Thought they either worked or the didn't. If one shorts, it cuts power to all 8, but the others will work if you pull the lead on the faulty one.

Process of elimination.. i have good fuel pressure so if no spark it's the coil/ dizzy; if there is a spark I'll pull one injector at a time to see which one is failing.

Thanks.

Tri458

All injectors are showing 15 ohms when cold and hot. Checked each injector terminal when engine running with a small 2-pin bulb and it flashes as it should. When hot, engine cuts out and no power to the injectors with the ignition on. Fuel pressure is fine and I have a good spark at the plugs. Disconnecting the throttle position sensor makes no difference. Any ideas please?

Tuned Performance

iTrader: (92)

KOEO now power to the injectors when the failure occurs ?

Tri458

KOEO? Sorry, don't understand.

When the engine cuts out, there is no power to the injectors. I have checked the fuses to the 2 set of feed wires from the ignition and they are intact so will trace the entire length of the wires to check there is no short.

Vader

KOEO - Key On, Engine Off.

If/when it occurs again, be prepared to test KOEO voltage at the main fuse panel INJ1 and INJ2 positions. If voltage is present there, check connection integrity at C221. C221 is a 6-position connector with a black plastic shell, arranged in two rows of three connections (A through F). The connector should be be hanging in the interior, originally near the center/right side of the vehicle, which may give you a clue to the length of the harness and how it may have been installed in the Apache.

If connections are sound at the C221 halves, consider the factory in-loom splices which Tuned alluded to.

Tri458

Key on engine off shows no voltage to the injectors. When engine cool off, it starts again.. I will check the wiring tomorrow, thank you.

Tri458

Just replaced the ignition control module but it's had no effect. Engine starts and revs well when cold but still cuts out after about 10 minutes.. When up to temperature. Smells like no fuel to the plugs, so injectors are not firing. When cold there is 12v to both terminals on the injectors. When it cut out there is no reading.

They will flash a light when the engine is running but not when cranking to start.

The injectors are wired from the fuse box which is live when the ignition is on and is wired to the accessory pin on the ignition. The fuel pump runs constantly as there is no take off for the pump on the harness but the relays etc are all wired in, as is the oil pressure switch.

Could this be the issue.

I have plugged in a spare 89 corvette ECM and it does the same, so assume the EcM is I
Ok

Is there a cut off switch to prevent the engine over- heating?

It's the only thing I can think of... Driving me nuts!

.. And fuel pressure is a constant 40 psi.

Vader

There is no factory thermal switch to cut injector pulses at high coolant temperatures, and no programming in the ECM to do that, either.

Since ignition pulses are being produced after the injectors shut down (you mentioned in Post #10 that it still has good spark) the distributor, pickup, reluctor, HEI module, EST, and other ignition devices are off the list of suspects. You now have a spare ignition module.

Again, when the injectors lose power after ten minutes of running, is there power at the fuse panel for the injectors? If not, look upstream toward the ignition switch or the bussing in the fuse panel. If there is power at the fuse panel for the injectors, look at the harness and connectors AFTER the fuse panel for the open circuit. Test this before acquiring any other replacement parts, or you may have a lot of other spares.

Tri458

Sounds like good advice, Vader. I have a new coil and pickup coil coming next week, so will fit them and try again... Process of elimination.

I read on another forum the pickup coil can be heat sensitive and can alter timing as well as interfere with the injectors?? One way to find out!

Problem here (UK) is parts are soooo expensive (3 items for the dizzy =£140 so far) and only a few companies know anything about the Chevy fuel injection cars... And charge a fortune!

Will advise on progress soon.. Thank you.

Vader

I must not be very clear in my communication.

In my assessment, it is NOT the pickup coil, and you probably have another spare part on the way. Nor is it the reluctor, EST, HEI, cap or rotor, coil, or anything else there. CLOSE UP the distributor and get away from there. If any of those items were at fault, there would be no spark when the engine stopped, and you indicated there IS spark.

Measure the DC voltage at the fuse panel when the engine dies and the key is on. Then go back and re-read Post #16. Share the results of your findings and we can get closer to the solution.

Tri458

No, you have been very clear, Vader, but I had already ordered the pickup coil etc, so will fit them anyway.

There is power to the injector fuse panel but I'm going to replace it anyway.

I found some poorly insulated factory splices in the injector harness yesterday, which I have repaired, but it still cuts out.

I'll keep you updated with my progress and thank you for your advice... Much appreciated.

Vader

What about the 6-way connector in the interior, C221?

Tri458

There is no 6-way connector as the wiring has been cut. The 2 injector leads and the fan wire were taped in a bundle and I have connected them to the fuse block coming off the ignition accessory post. Live with the ignition on.

ASE doc

Im sorry, Tri458, for not paying closer attention to this thread. It sounds like you replaced parts that weren't needed. I said "if there is no spark when the engine cuts out, replace the ICM".

Vader is absolutely correct. If there is spark, the ICM and the dist as a whole, are not the cause of your troubles. The few exceptions I have seen to this were cases where the ignition module continued to operate the ignition coil but lost the crank reference signal to the ECM. This would be obvious on a factory installation by the loss of fuel pump relay activation when cranking. On a scan tool, there would be no RPM signal. Also, if you had lost the ICM, you would have no injector pulse from the ECM when this problem occurs.

The loss of ignition power to the injectors when the system warms up is obviously a sign of some issue in the ignition power circuit between the battery and the injector power supply. If this were a factory 82-92 GM product, I would say to look for a faulty fusible link, poor connection at the starter batt+ terminal, or a fault in the ignition switch. Since this is a retro fit installation, the possibilities are more varied. It sounds like you've got some wiring issues if you have wires taped together.

Electrical tape has its uses, wrapping wire looms to keep things neatly in place, but it has no business serving as insulation and certainly never as a substitute for solder or proper crimp connections. My advice would be to start by reconnecting any circuit now connected with taped splices, using either solder and heat shrink tubing or with crimps using a good indent crimping tool like Klein makes.

Then, when you think you have these wiring problems fixed, perform a voltage drop test between the battery + terminal and the injector power circuit with the engine running. There might be 1 volt drop due to many connections and the ignition switch in between the two. As the engine stalls, see if the voltage across the two hasn't gone closer to 12 volts. Then break the circuit into sections. I would focus first on the ignition switch and then the fuse panel. Make sure that you aren't overloading any part of the system. My thought from reading your posts is that you probably are.

Tri458

Don't worry, ASE doc, at least if I replace these items I can be sure the dizzy is working fine. It's always good to have spares! I can now concentrate on the harness...

Just a thought... Could the EGR/ intake need cleaning? The plugs are black so running rich.. Or could this just be where it's not had chance to run long enough?

ASE doc

its possible if the engine is never warming up that the system may never get past warm up enrichment. its hard to diagnose a fuel trim issue on an engine that stalls after 10 minutes running. Focus first on the injector power supply problem. Once the stalling problem is solved, cleaning the EGR is never a bad idea if there is any concern of it sticking. Cleaning the intake is of questionable value. The only real benefit I see to it is removing deposits from the valves. If you do it just be careful not to hydrolock a cylinder.

Tri458

Will do. Thanks.

Tri458

New pickup coil and coil fitted. Whilst stripping the dizzy found the insulation cover on the 4 wires to the coil was missing, so stripped an old one I had in the garage and replaced it. Engine starts and idles really well now, much better than before but still cuts out after about 10 minutes and will not re- start. However.... Something I had not seen before happened. Fuel pressure dropped to zero and stayed there even when I could hear the pump running. Suddenly jumped back to 40 psi but would not start.

Could it be an air lock in the fuel rail/ pipes? Cavitation? As it's not a standard setup, the return line goes into a T connection between the tank and the filter, not back into the tank.

Checked power from the ignition to the fuse box, from the fuse box to the injectors and the blue and green earths into the ECU and have 12 volts everywhere. Ordered a set of noid lights to check the injectors properly.

Beginning to think its fuel starvation....

I'll get there eventually! Will update when I've checked.

Tri458

new module, pickup coil and coil fitted.

New fuel pressure regulator fitted.

Return fuel line now put back to the tank (was into the fuel line on a "T"
connector between the tank and fuel filter.)

Engine now runs for ages and does not cut out but if I turn it off with the
key, it will not re-start or even fire up.

12v showing on both pins of the injectors and 15-16ohm with the ignition on
but will not flash a node light when cranking over. 12 volts showing on the blue and green earth connectors to the ECU.

A good spark on the plugs.

Any ideas please?
Thanks

Alan.

Tri458

Engine now runs well but will not re- start when hot.. Tried everything. Will take out the new ICM tomorrow and check the install.. Just to be sure.

Still no spark on the injectors when cranking.

If it's the ECM, can I just replace the PROM or do I need to replace the whole unit? I put the old prom in my spare corvette ECM ( both 1227165 code) and it has the same problem, so am assuming it could be the PROM?

Tri458

Tested everything and all indications were the ECM was faulty.
Replaced the ECM and engine harness with a later MAP setup. Replaced the knock sensor, Map, idle intake motor (and reset it), coolant temp sensor at the front of the engine, ATS sensor but still cuts out after idling for about 5 minutes. Engine only gets up to about 180F.

Driving me nuts and making me very poor... Can anyone help please? Thanks.