258 tbi stalls out when hot

[CJ7Rubicon]

I have a 258 with tbi upgrade.It runs great until it warms up,then I hear a relay click and fuel dumps into the tbi until it dies.Once its dead the injectors continue firing and fuel pump stays running,unless I turn the key off.I have changed the ecm out and replaced the cts.

This is a fuel only system with a afi wiring harness and chip tuned to my motor upgrades.Msd 6al,larger ford cap and rotor,header,272 cam,bored 60 over,shaved head.In a 85 jeep cj7.It did run fine for 2 years.

Once while offroading the motor died and would not start back up.I had the key on while pulling it to the trailer and it melted the cap,rotor and coil.That might be unrelated but I dunno.It ran fine for a few months once I replaced those parts.

It has been suggested to try to run it with the cts unplugged but I have not tried this yet.

Thanks for any suggestions.

[Bill usn-1]

Go to the FAQ's and get the voltage check spread sheet in the wiring FAQ.

Then take the reading for key on and engine running when warm.

If you can log data then do that also per the FAQs.
BLM and log.

Sounds like a bad distr pick up when it get hot. Take an ohm reading when cold and then when hot.

You didn't say what distr your running to trigger the 6al.

I don't understand the burning up with the key on.

I would recommend dumping the 6al and going duraspark distr and the 4 pin GM module. Or better, switch to timing control and use the 8 pin module. But that's just me.

[CJ7Rubicon]

As far as I know its the stock distributor.Ill work on getting the program and cable to read the logs.Thanks,I will report back.

[Bill usn-1]

What is the stock distr?
I'm not a jeep guy.
We do IHs here.

[Caver Dave]

Originally Posted by CJ7Rubicon

Once its dead the injectors continue firing and fuel pump stays running,unless I turn the key off.

I had this exact issue on my 304 when trying to set the base timing w/ bypass unplugged! Engine would die, pumps still running/injectors firing... filling the venturi's FULL of fuel (scary!) until key turned to off. Through troubleshooting, found it was the EST being mounted 3/4" *ABOVE* the GM TBI coil (EMI/RFI interference?). Once they were separated a bit & the 3wires feeding it from the dizzy shielded (metallic wrap grounded on 1 end), it went completely away...

However, this application was both fuel & timing... and you're fuel only, so maybe my findings will help the experts diagnose?

Originally Posted by Bill usn-1

You didn't say what distr your running to trigger the 6al.

His description said "larger Ford cap" (larger dia. cap w/ terminals spaced further than the OEM cap, helping to negate cross-firing on hotter ignitions, like the Ford TFI, etc), so I'm guessing it's already the Motorcraft/"DuraSpark" dizzy?

While pretty dang ornery at times, JYG (formerly "TeamRush"), was among the first to document the TFI upgrade for Heeps, similar to your work with TBI swaps. I used his lists/diagrams to switch from points to electronic ignition about 10 years ago (boy, what a difference!)

Originally Posted by Bill usn-1

I don't understand the burning up with the key on.

I don't recall the specific's, but pretty common in certain scenarios (full 12VDC to coil requiring resisted power... 8-10VDC?). I lost a a couple coils like that...

Originally Posted by Bill usn-1

Or better, switch to timing control and use the 8 pin module. But that's just me.

Not just you brotherBill!
Fuel only leaves power (+ control & tune-ability) on the table... unless his 258 already has too much?

[CJ7Rubicon]

I will have time to work on it this weekend.The above is correct its the motocraft duraspark as far as I know.I thought I saw a link to the cable I need to build but Im still looking.

IF I get this heep running like it was,I will go with the timing control as soon as possible.

[Bill usn-1]

Keep in mind that dieing when hot is not typically a problem with the EFI.
It's possible that the fuel pump is going bad but it's more likely the ignition. When it dies you need to check for spark.
The EFI will not turn on the fuel pump or fire the injectors without spark.

[CJ7Rubicon]

Quick replies here!

Once it dies,it will start back up immediately,IF I hold it at wot to burn all the gas its dumping.If I try to feather the pedal back down it dies,continuing to flood out.It then has to cool back down before it will run on its own.But once its hot again,same thing over and over.

[Bill usn-1]

It's not an EFI problem.
Still sounds like ignition.

Bypass the MSD and run just the distr and ignition module if you can.
And measure the pickup cold and warm.