engine shutting down after going REALLY lean!?

Decipha's custom GUFX strategy covers all 89-93 foxbody ecu's including the 88 mass-air california ecus.
canuck1
Posts: 67
Joined: 2021 Mar 31, 17:29
Location: Victoria, BC CANADA
Vehicle Information: QH, TunerPro RT 5, GUFX_220418.xdf, A9L2_220405, DECIPHA_220505.ADX, 395w, AFR 195CC Renegade heads, Comp XE274HR cam, Siemens-Deka V 80lb/hr (shorties), Mass-Flo-EFI style 4bbl throttle body with GM maf on top. Custom long tube headers, sidepipes, 5 spd manual.

engine shutting down after going REALLY lean!?

Unread post by canuck1 »

I am really happy with how my car is running with the correct injector data, Fuel finally pretty darn good, and now THIS!?

While pulling away from the gas station, just put it into 2nd at LOW speed and it feels alsmost like someone has turned off the ignition key. Both hegos dropped down to the basement (car keeps rolling, but no power, engine seems OFF). I push the clutch in to keep her rolling, ease it out to see if it will restart but NO. I quickly switch key off, then back on, release clutch and it jumps back to life as if nothing has happened.

Looking at the log I can see it went REALLY lean (verified by fuel error % and HEGOS at lowest voltage) but I'm guessing that was because there was NO fuel available!? It continues to start and run fine but it has done this to me several times now. I don't want a trip home on the ramp truck, so figure I'd seek some help from someone who may have seen these symptoms before? Battery is new, checked all main chassis & engine grounds, alternator is putting out good voltage, fuel pump runs and makes good pressure but something (I believe) is either turning the pump off or cutting power to the injectors intermittently. Anybody want to take a shot at what might be happening??

Here's a screen shot of my running state monitor and dashboard logged while the problem was occuring. Thanks for any help you can offer.

Sean

shutting off hegos.jpg
shutting off hegos dash .jpg
decipha
Posts: 4950
Joined: 2021 Feb 15, 12:23
Location: Metairie, LA
Vehicle Information: Work Truck
'19 F-150 3.3L

Re: engine shutting down after going REALLY lean!?

Unread post by decipha »

graphs doing nothing for me as im a playback or data type person

in any case its definitely fuel

step 1 when diagnosing any intermittent issue on eec-iv is to replace the fuel pump relay and the ecu relay.
canuck1
Posts: 67
Joined: 2021 Mar 31, 17:29
Location: Victoria, BC CANADA
Vehicle Information: QH, TunerPro RT 5, GUFX_220418.xdf, A9L2_220405, DECIPHA_220505.ADX, 395w, AFR 195CC Renegade heads, Comp XE274HR cam, Siemens-Deka V 80lb/hr (shorties), Mass-Flo-EFI style 4bbl throttle body with GM maf on top. Custom long tube headers, sidepipes, 5 spd manual.

Re: engine shutting down after going REALLY lean!?

Unread post by canuck1 »

Thanks,

Prob good idea to focus on FP relay, since the ecu seemed to continue to spit out data after it engine cut out.

Sean
red5.0fogger
Posts: 148
Joined: 2021 Mar 22, 15:58
Location: Newington CT
Vehicle Information: 1986 Mustang GT, Stock block, TFS 170 Heads , N41 cam, ported cobra intake, nitrous, T5 , 3.73s

Re: engine shutting down after going REALLY lean!?

Unread post by red5.0fogger »

sounds like there might be quite a bit of water in the fuel from the station. Water would be like an off switch. Then as it sloshes around it gets better or worse.
canuck1
Posts: 67
Joined: 2021 Mar 31, 17:29
Location: Victoria, BC CANADA
Vehicle Information: QH, TunerPro RT 5, GUFX_220418.xdf, A9L2_220405, DECIPHA_220505.ADX, 395w, AFR 195CC Renegade heads, Comp XE274HR cam, Siemens-Deka V 80lb/hr (shorties), Mass-Flo-EFI style 4bbl throttle body with GM maf on top. Custom long tube headers, sidepipes, 5 spd manual.

Re: engine shutting down after going REALLY lean!?

Unread post by canuck1 »

Hmm, never thought about fuel contaminants. Could be, I guess? It does seem more electrical in nature though, since it responded immediately to switching key off and back on. Didn’t happen again during the 4 mi drive back home. I’ll replace the fuel pump relay tonight and test, if rain stays away. I hate troubleshooting intermittent problems!
decipha
Posts: 4950
Joined: 2021 Feb 15, 12:23
Location: Metairie, LA
Vehicle Information: Work Truck
'19 F-150 3.3L

Re: engine shutting down after going REALLY lean!?

Unread post by decipha »

your not going in to overheat protect are you?
canuck1
Posts: 67
Joined: 2021 Mar 31, 17:29
Location: Victoria, BC CANADA
Vehicle Information: QH, TunerPro RT 5, GUFX_220418.xdf, A9L2_220405, DECIPHA_220505.ADX, 395w, AFR 195CC Renegade heads, Comp XE274HR cam, Siemens-Deka V 80lb/hr (shorties), Mass-Flo-EFI style 4bbl throttle body with GM maf on top. Custom long tube headers, sidepipes, 5 spd manual.

Re: engine shutting down after going REALLY lean!?

Unread post by canuck1 »

I don't think it's related to overheat protection. Hottest it ever gets is 190 ECT, mostly runs between 185-190 ECT. ACT is in the manifold though, it can get over 160 when pushing it but when the specific shut down that happened above, ECT was 178, ACT was 146.

Sean
decipha
Posts: 4950
Joined: 2021 Feb 15, 12:23
Location: Metairie, LA
Vehicle Information: Work Truck
'19 F-150 3.3L

Re: engine shutting down after going REALLY lean!?

Unread post by decipha »

yeah then fuel pump and ecu relays it is
canuck1
Posts: 67
Joined: 2021 Mar 31, 17:29
Location: Victoria, BC CANADA
Vehicle Information: QH, TunerPro RT 5, GUFX_220418.xdf, A9L2_220405, DECIPHA_220505.ADX, 395w, AFR 195CC Renegade heads, Comp XE274HR cam, Siemens-Deka V 80lb/hr (shorties), Mass-Flo-EFI style 4bbl throttle body with GM maf on top. Custom long tube headers, sidepipes, 5 spd manual.

Re: engine shutting down after going REALLY lean!?

Unread post by canuck1 »

Following up.

I pulled and tested function and resistance of the fuel pump relay, nothing stands out as being wrong with it. It may be environmental factors that affected the relay’s function. My heater core is behind the center of my dash and relays are mounted together on the back of the firewall, not far from heater core. It may be that heat soak from sitting at the gas station raised ambient heat enough to affect the ability of the relay to stay engaged? I changed it out in any case, and moved my relay bundle farther away from the heater core. Seems fine now, whatever caused the issue previously.

Sean
canuck1
Posts: 67
Joined: 2021 Mar 31, 17:29
Location: Victoria, BC CANADA
Vehicle Information: QH, TunerPro RT 5, GUFX_220418.xdf, A9L2_220405, DECIPHA_220505.ADX, 395w, AFR 195CC Renegade heads, Comp XE274HR cam, Siemens-Deka V 80lb/hr (shorties), Mass-Flo-EFI style 4bbl throttle body with GM maf on top. Custom long tube headers, sidepipes, 5 spd manual.

Re: engine shutting down after going REALLY lean!?

Unread post by canuck1 »

Still happening. Worst ever on a really hot day, shuts off on the highway, comes back with key off/on and dropping the clutch. Happened 3-4 times in one day in various circumstances.

I lowered the relay block from behind the dash (no longer anywhere near my heater core) and they seemed surprisingly hot to the touch. My thoughts went to contact corrosion but all seems clean. I think it could be a irregular ground connection, as I thought that might make the relays run unnecessarily hot? I know a failing fuel pump can put excessive load on the relays too. Any chance this indicates a problem with the actual computer, since it is responsible for signalling the relays to change state??

Sean
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