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| Slant 6 stalls - has spark & fuel, won't fire https://www.slantsix.org/forum/viewtopic.php?t=67317 |
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| Author: | Dead Reckon [ Tue Jun 27, 2023 3:06 pm ] |
| Post subject: | Slant 6 stalls - has spark & fuel, won't fire |
The factory original, probably high mileage Slant 6 in my '83 D150 backed by an A-833 4 speed has a recurring issue where after long periods of idling or coasting, unless you feather the gas pedal bringing the RPMs up before takeoff, the truck will stall and is really hard to get started again. The truck has a new cap and rotor, the old rotor contact got bent on the cap button somehow, the plug wires and plugs are good, the ignition box and coil are new too. It has a Carter BBD on a 1 to 2 barrel adapter with a manual choke setup. The truck will start up and run fine once it warms up, but after that if I let it idle or coast too long, if I'm not revving it and riding the clutch a bit she'll just die and won't start. When she does this eventually she billows smoke up out of the engine, she'll backfire once or twice and if I hold the throttle just right after the engine farts out a magical cloud that makes people think my truck is on fire, she'll eventually rev to life. I have noticed a bit of vertical slop in the distributor when replacing the cap, the reluctor can move probably nearly a quarter inch up and down, I haven't noticed spark issues or it losing spark, but could the play in the distributor be part of the problem? It isn't losing spark, or fuel, it just wont' start. When this truck is running it runs great, it just really hates idling. I have a new intake / exhaust gasket I'm gonna install Friday, cause I know that's blowing exhaust up out of the manifold, but I'm at my wits end here. She's got spark, fuel, no go until it uh, wants too? The coolant is full and green, not losing any, oil is dirty but so is the engine, PCV isn't stuck open, neither is the vacuum valve for the brakes. No vacuum leaks I can find at all. I am really confused here guys, help would be nice. |
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| Author: | Greg Ondayko [ Tue Jun 27, 2023 3:54 pm ] |
| Post subject: | Re: Slant 6 stalls - has spark & fuel, won't fire |
I would hazard a guess to fuel vapor lock in the line between the pump and carb or bad/ sloppy timing set or both. Maybe start with the Fuel Line Modification. |
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| Author: | Dead Reckon [ Tue Jun 27, 2023 4:03 pm ] |
| Post subject: | Re: Slant 6 stalls - has spark & fuel, won't fire |
Quote: I would hazard a guess to fuel vapor lock in the line between the pump and carb or bad/ sloppy timing set or both.
Fuel line doesn't seem like it's getting that hot, timing I got no idea about. I've actually got my own metal line routed in a way it shouldn't be getting hot. Maybe start with the Fuel Line Modification. An exhaust leak between the exhaust manifold and intake manifold could cause vapor lock though, couldn't it? |
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| Author: | Greg Ondayko [ Wed Jun 28, 2023 4:51 am ] |
| Post subject: | Re: Slant 6 stalls - has spark & fuel, won't fire |
If you have rerouted the fuel line somehow above the engine and away from heat, then it is probably not that. It's also possible that the fuel pump could be working intermittently(doubtful) but maybe throw another one there and see if the issue persists. Possibly there is some dirt / trash in the carb blocking things up, causing the conditions you observe. |
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| Author: | Dead Reckon [ Wed Jun 28, 2023 5:38 pm ] |
| Post subject: | Re: Slant 6 stalls - has spark & fuel, won't fire |
Quote: If you have rerouted the fuel line somehow above the engine and away from heat, then it is probably not that.
I have been suspicious of the fuel pump, it was on the truck as it sat for 10 years but most of the time it seems fine, starts fine, runs fine. The carb is fine, I checked it and it was rebuilt off a 318, it's a Carter BBD, I think I mentioned that. The fuel line I have routed probably 3" off the top of the valve cover, I need to make a bracket from the valve cover to the line to make it not vibrate as much but it's metal down behind the alternator then rubber line just above the stock return style metal fuel filter, which I replaced. The fuel tank was very clean in this truck despite sitting 10 years, I used a mechanical pump to pull fuel out, it had gone bad but there wasn't any crud building up using one of those clear plastic filters to check it. It's also possible that the fuel pump could be working intermittently(doubtful) but maybe throw another one there and see if the issue persists. Possibly there is some dirt / trash in the carb blocking things up, causing the conditions you observe. Now I'm wondering if my heat riser is stuck in the exhaust manifold or something, I have a gasket set, and a thick spacer gasket between the 1bbl to 2bbl adapter, plus the thing is like 3" tall, and gets plenty of air to stay cool, the carb never seems hot enough it should boil, and believe me I have experience with those. I even have the return from the BBD plumbed into the charcoal canister as it would be on the 318. I am going to try and replace the exhaust / intake manifold gasket Friday morning, my day off, I'm having trouble with the exhaust studs but I'll post another thread about that. I'm really hoping the answer is just exhaust getting into the intake, I've seen that on a friends '77 D100, cool little truck, 4x4 step side. Dunno though, with the corn liquor they pass for fuel nowadays it could be anything. |
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| Author: | volaredon [ Thu Jun 29, 2023 4:05 am ] |
| Post subject: | Re: Slant 6 stalls - has spark & fuel, won't fire |
No you're NOT getting exhaust into the intake unless your egr is stuck wide open. |
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| Author: | Dead Reckon [ Thu Jun 29, 2023 9:17 am ] |
| Post subject: | Re: Slant 6 stalls - has spark & fuel, won't fire |
Quote: No you're NOT getting exhaust into the intake unless your egr is stuck wide open.
Didn't think about that, could be, kind of scared to mess with the bolts.
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| Author: | Dead Reckon [ Fri Jun 30, 2023 11:25 am ] | ||
| Post subject: | Re: Slant 6 stalls - has spark & fuel, won't fire | ||
I feel like an idiot, I should've checked the spark plugs, ordered some new ones, but the ole Amazonia is saying it's gonna be a few weeks, I guess my 23 year old puddle jumper Nissan Sentra (Dentra) is gonna be getting driven, oh well, she's a 5 speed and the AC works. The truck keeps vapor locking so bad, and I know these plugs aren't helping, I don't know if new ones will help but, it's worth a try for $20
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| Author: | Dead Reckon [ Tue Jul 11, 2023 8:19 am ] | |||
| Post subject: | Re: Slant 6 stalls - has spark & fuel, won't fire | |||
Figured out the issue, I should've checked this from the start but it's been a minute since I've worked on one of these trucks. The ballast resistor is bypassed, overvolting the coil. I couldn't find the bypass so I just added another ballast in line. However I also discovered that neither the new coil I had on the truck nor the one that came on the truck would run on 7 volts, at all, they'd start fine on 12 but not run on 7. I took an old Mopar ignition coil off the 318 I have set aside for this truck, part #4176009 / 411468, it runs happily on 7 volts with an inline ballast resistor, so that's my solution for now. This has not been fun, but it has taught me I need to remember the basics and check things like voltage, all the old cars / trucks I've owned and this is what got me.
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