EFIDynoTuning Forum

1994 bronco with Moates QH.

Hello all, wondering if you all may have a suggestion before I start testing everything.

I recently had an issue with the truck. One night it started running rough on a short ride home. The next day it wouldn’t start. I was sure the QH battery had died as it has been installed for many years. I pulled codes and got a 511 PCM ROM error which reinforced that idea. I pulled the ECM and sure enough the QH coin battery was dead (measure with meter). Replaced it and reinstalled. I uploaded the last bin file I received to the QH and still have a crank but no start situation. I’m still getting a 511 code for PCM ROM error. I tested the TFi module just to be sure and it tests fine and is receiving signal from the distributor. I have good fuel pressure.

Before I get too involved, is there anything simple I could be missing after replacing the QH battery and re-uploading the bin file?

Thanks all!

Disregard… re-rested the battery and it had almost 3v so it must be something else. I can’t delete this, but Mdisregard.

The QH shouldn't lose the tune with the engine on. Even if the 3v died. also with the 3v dead you can run it off the laptop, serve the tune and bingo. Seems like something else happened.

Thank you, I have spark, coil is good. Good fuel pressure but I just tested the injector signal with a noid light and I’m not getting any signal to the injectors. Power to the pcm is good. Down the rabbit hole I go!

red5.0fogger wrote: ↑2026 Apr 09, 10:27 The QH shouldn't lose the tune with the engine on. Even if the 3v died.

Interesting. I was out recently and my engine stopped dead and wouldn’t start. After about 30mins it fired up again. Stopped after idling for about 3 mins.

I assumed it was the QH battery (probably about 5 years old so will replace anyway) but this sounds like something else as well. Yikes!

Yes I found some bad traces in the ECU so I ordered a replacement used unit and I’m going to try that first. I found that I was getting injector pulses but they were far too weak to trigger the injectors. Using an old injector tester I have they fire, but despite seeing flashes (weak) on the noid light they weren’t clicking. Hoping the ECU just didn’t have a strong enough ground signal to fire them and it will be a simple fix… I have spark and I know the timing hasn’t changed. I have good FP on a gauge, so im narrowing it down to being injector related.

Cool, Ur gonna get it!

that usually means your ecu relay is weak

the ecu fires the ground not the positive

make sure your ignition switch isnt weak either

can verify by jumping the injector positive to battery

Excellent suggestions thank you!

Still no luck. I seem to have spark albeit maybe not strong, injectors are firing as the plugs are wet and the noid light is flashing just not audibly clicking. Dist pip signal is there and TFI tests ok. This is confusing.

One question, regardless of tune, while it wouldn’t run well, the pcm should attempt to fire everything without the QH installed correct?

Bummed I was going to try and hit a big bronco event in TN this weekend. Looks like it’s not happening.