Author Topic: Is my AFM bad?  (Read 564 times)

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Tumbler510

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Is my AFM bad?
« on: Feb 13, 2019, 09:27:11 AM »
1989 22RE, just finished the timing chain (and accessory) replacement, and can;t get the truck to turn over.
I checked and rechecked everything, all connections were good.
I realized the fuel pump was suspiciously quiet, and that the truck wasn't turning it on.
I shorted it using the test block, and the FP came on fine.
I shorted the connector into the AFM, and the FP when on when they key was turned.
Is there something I am doing wrong, or is the AFM busted?

My AFM:

Slabzilla

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Re: Is my AFM bad?
« Reply #1 on: Feb 13, 2019, 11:21:58 AM »
Is the ground strap at the intake joint under the upper manifold connected?  Won't even burp without it, goes on the center bolt.  :twocents:
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Tumbler510 [OP]

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Re: Is my AFM bad?
« Reply #2 on: Feb 28, 2019, 08:24:57 PM »
Is the ground strap at the intake joint under the upper manifold connected?  Won't even burp without it, goes on the center bolt.  :twocents:

Good call. I checked all grounds with my multimeter, and they were all continuous, and under 3 ohms, so those should be good.
Here's a video of it trying to turn over.

https://www.youtube.com/watch?v=MILcW7xEJEk

RASALIBRE

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Re: Is my AFM bad?
« Reply #3 on: Mar 01, 2019, 06:40:32 AM »
Was your afm connected to a 90į elbow off the throttle body facing straight down before all this maintenance?
Thatís what Iím seeing in the video you posted.
Youíre fighting gravity. The afm flap/door isnít able to open.

gnob

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Re: Is my AFM bad?
« Reply #4 on: Mar 01, 2019, 06:47:06 AM »
It should still fire momentarily from the CSI.  when you open the flap with key on, the pump should run.
hold this. . .

Tumbler510 [OP]

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Re: Is my AFM bad?
« Reply #5 on: Mar 01, 2019, 09:02:12 AM »
Was your afm connected to a 90į elbow off the throttle body facing straight down before all this maintenance?
Thatís what Iím seeing in the video you posted.
Youíre fighting gravity. The afm flap/door isnít able to open.

Yes it was, but I was always confused by this configuration. The AFM that came with the truck was broken during tear down (undoing the screws for the connector and pulling wasn't the best way to remove the connector....super helpful friends...) so this one has never run on the truck before.

Would it help to diagnose if i had it going horizontal instead of vertical and try to start up that way?

Tumbler510 [OP]

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Re: Is my AFM bad?
« Reply #6 on: Mar 01, 2019, 09:02:52 AM »
It should still fire momentarily from the CSI.  when you open the flap with key on, the pump should run.

OK, so you're suggesting I manually open the flap when starting to verify the circuit?

gnob

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Re: Is my AFM bad?
« Reply #7 on: Mar 01, 2019, 09:42:54 AM »
Key on, finger flap. Pump should run.
hold this. . .

Tumbler510 [OP]

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Re: Is my AFM bad?
« Reply #8 on: Mar 01, 2019, 02:22:25 PM »
Key on, finger flap. Pump should run.

Jackpot. I removed the 90* elbow, and ran the AFM detached from the TB. I could hear the pump go on once the plate was depressed.

Then I placed a small weight on it, and when the system was pumping, I attempted to turn it over. No dice. It still sounds like it did in the above video...

OVRAROK

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Re: Is my AFM bad?
« Reply #9 on: Mar 01, 2019, 02:29:23 PM »
Video sounded like no spark...
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Tumbler510 [OP]

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Re: Is my AFM bad?
« Reply #10 on: Mar 10, 2019, 06:29:15 PM »
Video sounded like no spark...

Props to your fine-tuned ears. I ordered a spark plug tester light, and it shows no spark to the plugs.
I've never dealt with an electrical system like this, so I assume I need to figure out if the coil is producing voltage to the distributor and then go from there, right?

Can I plug the spark plug tester into the inlet of the distributor for that or if there a different test that would be better?

Snowtoy

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Re: Is my AFM bad?
« Reply #11 on: Mar 11, 2019, 04:31:32 PM »
From my 90 FSM
AFM






Spark test



Since the issue all occurred after the T-chain removal/replacement, I would start with the basics, recheck all wires, fuses, connections, etc., timing, then go on from there.
« Last Edit: Mar 11, 2019, 04:46:45 PM by Snowtoy »
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