Starting and Acceleration Issues

[Low fat]

Unless by some freakery it's accessing liquid fuel - or some other weirdeness. The engine running with the fuel supply disconnected is as yet unexplained.



Full agreement on that.



IMO the FPRs can stick.
Pretty sure that was the cause of my fuelling issue last year. Running on LPG the FPR was returning all the fuel back to the tank so would have been pushed wide open. And I think it stuck there so when I tried to start it on gasoline there wasn't sufficient pressure at the nozzles. That the fuel system came good after a sizeable inlet backfire (on LPG) was it being shocked closed I think. No problem since and to avoid repetition of it I installed a pump cut-off switch.



I once had a frog (in bits) come through a kitchen tap despite the holes in the source strainer being smaller than frog size - but not spawn. Getting a bit off-topic here though - not helping the OP!

Replace the fuel pressure regulator and coolant temp sensor

 

[HotWheelsBurban]

Replace the fuel pressure regulator and coolant temp sensor

The coolant temperature sensor in the intake manifold just below the thermostat housing controls the mixture, especially on startup when the engine is in open loop. If the coolant is nasty, or there is crud in the system, it can cause electrolysis and this damages the sensor.
I ran my Burb with water for a few months and this has happened to my truck's sensor. So I have to give it a tap on the throttle at startup, and let the fuel pressure prime a few seconds when it's been sitting for a few hours ( or first start of the day).
I know it needs the spider changed ( this includes a new FPR), but I'm saving $$$ for that. Want to do all the top end stuff at once. Just put new plugs in Saturday morning and that took care of most of the missing. Hope to get plug wires done this weekend.

 

[Marcos Beltran]

So i know for sure the coolant temp sensor was bad. Tested it with my multimeter and seen the live data on the scanner which read -40°. Replaced part and had a normal reading of 20°. But now the truck wont start at all. Not even with the magical mysterious method, lol. Whats worse is now im not getting any codes. Will a failed/stuck FPR throw a code?

 

[Pinger]

Will a failed/stuck FPR throw a code?

Not itself, it is purely mechanical. It would take a symptom of it screwing running up to throw a code.

So i know for sure the coolant temp sensor was bad. Tested it with my multimeter and seen the live data on the scanner which read -40°. Replaced part and had a normal reading of 20°. But now the truck wont start at all. Not even with the magical mysterious method, lol. Whats worse is now im not getting any codes.

Try the old one again? You wont have to refit in position just connect (and ground it if it needs a ground).
If it was fooling the ECU into thinking the temp was -40(C?) then it must need plenty of fuel to start.
There's also an inlet air temperature measurement. How does the ECU reconcile such a discrepancy? The coolant can never really be colder than ambient air (though the reverse is true).

 

[Marcos Beltran]

Not itself, it is purely mechanical. It would take a symptom of it screwing running up to throw a code.



Try the old one again? You wont have to refit in position just connect (and ground it if it needs a ground).
If it was fooling the ECU into thinking the temp was -40(C?) then it must need plenty of fuel to start.
There's also an inlet air temperature measurement. How does the ECU reconcile such a discrepancy? The coolant can never really be colder than ambient air (though the reverse is true).

It wasnt starting with the old one either anymore that was the reason for me pursuing that avenue even further. Figured if i fix that than that must be the problem. Well it wasnt. So now im getting a P0102 Mass or volume air A circuit low and a P1351 ignition coil control circuit high voltage. The thing is i was not getting any codes for a while. I disconnected the MAF sensor and reconnected it and then that came on. I also was checking for spark with a little bypass tester light between the spark plug and wire and now the P1351 code came on. So i dont know if that was direct consequence of what i did or if that was about to rear its ugly head anyways. I would think thats a hell of a coincidence if it was. Back to square one. So i guess im about to do a spark plug and a wire change next. I know thats not the problem but it needs to be done anyways.

 

[Pinger]

It wasnt starting with the old one either anymore that was the reason for me pursuing that avenue even further. Figured if i fix that than that must be the problem. Well it wasnt. So now im getting a P0102 Mass or volume air A circuit low and a P1351 ignition coil control circuit high voltage. The thing is i was not getting any codes for a while. I disconnected the MAF sensor and reconnected it and then that came on. I also was checking for spark with a little bypass tester light between the spark plug and wire and now the P1351 code came on. So i dont know if that was direct consequence of what i did or if that was about to rear its ugly head anyways. I would think thats a hell of a coincidence if it was. Back to square one. So i guess im about to do a spark plug and a wire change next. I know thats not the problem but it needs to be done anyways.

I spent last Sunday and Monday with a no-start condition. I also got 'P0102 Mass or volume air A circuit low' and when I looked for 12V on the pink wire to it it wasn't there until I re-instated a missing fuse (ENG-1, 20A mini in the FRC). The absence of that fuse never stopped it running (affected the transmission though) but with it installed the O2 sensors (heating elements) and EVAP system now have correct feeds.
Check for voltage on the pink wire going into the MAF. There should be a solid 12V there. Ditto the pink wire on the coil.

I don't know what ' P1351 ignition coil control circuit high voltage' actually means - struggling with the notion of a 'high' voltage but possibly it was triggered by testing for spark. If you have a multi meter I'll find resistance values for you to check on the coil and post them.

I don't know if this applies to our trucks or not but on smarts disconnecting the battery for 30s allows the ECUs (PCM in GMT400 speak) to re-boot. Gets rid of anything in there caused by faulty sensor readings. Perhaps someone can advise if this is worth doing in light of your PCM seeing spurious irreconcilable signals from the coolant sensor.

 

[Pinger]

The problem with pushing the Schrader valve to see if there's fuel there still doesn't tell you if you have high enough pressure. You may have fuel volume, but I think you need like 55 psi (?) to actually overcome the spring pressure on the poppet valves.

.

In absolute terms - I agree.
But, in the scenario where it is running (assume adequate fuel pressure) then quits, if there was still the same fuel pressure then a healthy spurt from the test port will ensue. If the fuel pressure had dropped significantly and killed the engine then no spurt.

Not an absolute test as the pressure dropping just below the required nozzle pressure will show fuel at the test port but if the pressure drop is of the magnitude associated with an electrical/pump failure then it is of use as an ad hoc test. It banks on pressure failures being nearly absolute - not partial.

 

[HotWheelsBurban]

I spent last Sunday and Monday with a no-start condition. I also got 'P0102 Mass or volume air A circuit low' and when I looked for 12V on the pink wire to it it wasn't there until I re-instated a missing fuse (ENG-1, 20A mini in the FRC). The absence of that fuse never stopped it running (affected the transmission though) but with it installed the O2 sensors (heating elements) and EVAP system now have correct feeds.
Check for voltage on the pink wire going into the MAF. There should be a solid 12V there. Ditto the pink wire on the coil.

I don't know what ' P1351 ignition coil control circuit high voltage' actually means - struggling with the notion of a 'high' voltage but possibly it was triggered by testing for spark. If you have a multi meter I'll find resistance values for you to check on the coil and post them.

I don't know if this applies to our trucks or not but on smarts disconnecting the battery for 30s allows the ECUs (PCM in GMT400 speak) to re-boot. Gets rid of anything in there caused by faulty sensor readings. Perhaps someone can advise if this is worth doing in light of your PCM seeing spurious irreconcilable signals from the coolant sensor.

I want to say on the 400 series trucks it takes 5 minutes of battery being disconnected, but I'm not entirely sure. Haven't had to do it in a while....
On my Burb, the CEL is on, and I thought that my friend at o'Reilly cleared the codes and turned it off on Sunday when she checked it with their scanner. She said there were no active codes, but the stored ones were still there. Didn't get the numbers though.
It does run better with the new spark plugs and coil wire though! Hoping to get new plug wires and my new United Motor Products distributor cap on this weekend if it doesn't rain all weekend....

 

[PlayingWithTBI]

I want to say on the 400 series trucks it takes 5 minutes of battery being disconnected, but I'm not entirely sure

You can disconnect the negative cable from the battery and short it to the positive cable, for a few seconds, to drain all of the capacitors. Then hook it back up, you should be good to go.

 

[jaywestfall]

I want to say on the 400 series trucks it takes 5 minutes of battery being disconnected, but I'm not entirely sure. Haven't had to do it in a while....
On my Burb, the CEL is on, and I thought that my friend at o'Reilly cleared the codes and turned it off on Sunday when she checked it with their scanner. She said there were no active codes, but the stored ones were still there. Didn't get the numbers though.
It does run better with the new spark plugs and coil wire though! Hoping to get new plug wires and my new United Motor Products distributor cap on this weekend if it doesn't rain all weekend....

Just out of curiosity, what plug wires are you going to us? I've bought MSD 8.5mm for mine.