AMC 401 / fuel only 454 TBI no start

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yossarian19
MS/Extra Newbie
Posts: 18
Joined: Sun Nov 12, 2017 9:54 pm

Re: AMC 401 / fuel only 454 TBI no start

Post by yossarian19 »

Well. With the time, effort and few bucks I've invested (more time than anything) I'm at serious risk of falling for the sunk cost fallacy - where we convince ourselves that with all we've put into something so far, it's worth it to see it through (even when it's really, really not)
I also hate for this to be another of those threads some future MS'er will read through before realizing that I never solved their problem, either.
But screw this.
I've already put too much effort into trying to keep the OEM (and crappy oem at that) ignition. Rick I can't thank you enough for your time and expertise trying to help. I wasn't ready to hear it when you said "Go crank trigger" but I am now.
I'm buying a 36-1 wheel & threaded hall sensor + some junkyard 5.3 coils and wiring.
All I can say to anyone reading this because they are having the same issue is good luck and maybe "cut your losses"
rickb794
Super MS/Extra'er
Posts: 6155
Joined: Sun Dec 21, 2008 10:28 am
Location: Portland OR

Re: AMC 401 / fuel only 454 TBI no start

Post by rickb794 »

I hope you will not be discouraged if the problem turns out to be associated with the TBI, the low impedance injectors can cause noise problems.

To see if they are the problem you generally disconnect the injectors and see if it runs on spray cleaner.

But since you were fuel only that is not a valid test.
Correctly identify your MS ecu here
Read the Do's and Don'ts to avoid the common pitfalls before starting your install or asking for help
Use only these manuals other manuals may cause brain damage or worse.
yossarian19
MS/Extra Newbie
Posts: 18
Joined: Sun Nov 12, 2017 9:54 pm

Re: AMC 401 / fuel only 454 TBI no start

Post by yossarian19 »

Well, I took a data log with the injectors disconnected. ~19 seconds of cranking, 22 sync losses. Seemed to happen at a pretty regular 0.4 second interval at around 150 RPM. I haven't done the math to see what that might correspond to in terms of engine events. I can't think why the test wouldn't be valid; the tach signal is still bad even without the injectors firing.
I'm going to let this sit for a while, actually, before spending any money or making big choices. A guy locally has an HEI distributor for this thing with a tach output line from the module - I might see how that works. Heck of a lot better than the stock ignition and might even produce a usable signal.
rickb794
Super MS/Extra'er
Posts: 6155
Joined: Sun Dec 21, 2008 10:28 am
Location: Portland OR

Re: AMC 401 / fuel only 454 TBI no start

Post by rickb794 »

Did you ever get this going?
Correctly identify your MS ecu here
Read the Do's and Don'ts to avoid the common pitfalls before starting your install or asking for help
Use only these manuals other manuals may cause brain damage or worse.
yossarian19
MS/Extra Newbie
Posts: 18
Joined: Sun Nov 12, 2017 9:54 pm

Re: AMC 401 / fuel only 454 TBI no start

Post by yossarian19 »

Whoops. Missed this.
I changed threads somewhere along the way as my question morphed with new data.
basically, the no start 'appears' to have been caused by a bad firmware flash.
What happened was I couldn't figure it out and sent the ECM off to be modified to direct coil control, along with the back story. The tuner, KP I think in pennsylvania, re-loaded the firmware and got a good coil driven signal. I told him to go ahead anyway and now I run a crank trigger ignition.
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