Bought an 81 D150 - some questions

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Old 05-21-2024, 10:56 AM
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In the past your choke wasn't opening. When cold the choke was closed and fired right up but unfortunately didn't open. With the choke not opening on restarts the choke forced more fuel to be sucked down the carb. For choke/carburetor engines the following works on most
Cold engine
1 Pump gas at least once maybe twice to close choke and have accelerator pump squirt fuel down the carb.
2. Once started cold allow on high idle for 30 seconds or so and tap once to knock idle down slightly. (Very high choke idles can break the ear off the first/reverse band when placed in reverse.)
3. On warmup while driving you may feel a slight hesitation when stepping on the gas. This is normal
Warm engine
1.Slightly depress pedal and crank
2. If no start try one or two pumps and retry
3. If none of the 2 steps worked, it may be slightly flooded and a full throttle start to clear it may be needed. Never over-rev an engine in neutral.
.
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Abcdefghii (05-21-2024)
Old 05-21-2024, 01:54 PM
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Good info to have, seems like I need to also press the gas pedal slightly with it cold, or at least I did earlier. Last Thursday that was not necessary, however if that's all I need to do to get it started, it's fine by me.
Old 05-22-2024, 05:36 PM
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Used the truck for some actual truck things today, 14 bags of top soil and some fence posts. Ok, I likely could have got all that easily in the Volvo, but that's beside the point, nice warm day out and driving the truck was more fun.

Not entirely without drama though, stopped at a relatives shop to pay for an oil change on my wife's vehicle, went to start and of course, no start again. Went back in and asked for some assistance and deduced that it appears to be getting vapor locked, pumped the pedal twice and then holding the pedal to floor got it started again. So I decided to risk heading to Lowe's.

What I did realize though, in my test yesterday I had the gas cap slightly loosened. When I parked at Lowe's, I loosened it again and was met with several seconds of vapor being released from the tank, I'm talking what felt like easily 10 seconds. Finished shopping, cap still just slightly loose and it started fine. Tightened the cap back up and went on my way, stopped at in laws to pick up my son, loosened the cap and again a ton of pressure releases. But, it then started just fine. I left the cap loosened on the drive home and have no issues with driving.

I'm 99%, maybe less, sure, that the tank not having a vent is causing the issues. I had bought a cap that specifically stated pressure and vacuum relief, but it seems that's grossly inaccurate. I think need to figure out adding a vent to the tank, the original vent line is under the truck and runs up to the engine bay, but the charcoal canister is long gone. It's possible I could use that, assuming I use some rubber fuel line from the tank to the line running to the engine bay. Not sure I want fuel vapor being released into the engine bay though...but I do think I need a vent on the tank.
Old 05-23-2024, 05:22 AM
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I'm a bit confused as to why it's building pressure. Vacuum yes. The fuel being pumped out creates a void which causes the vacuum. Pressure is confusing. All tanks need a vent or some type of circulation to work. You are right, fumes should not be forwarded to the engine compartment. I'd contact the manufacturer of the tank and see what they say about the problem.
Old 05-23-2024, 05:54 AM
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It may be vacuum and since I see the fumes coming out and hear the hissing, then I assume it is pressure. Possible that as the air is being sucked in (vacuum) that the fumes are being displaced and pushed out which makes me think it is pressurized. Either way, I do think that getting some kind of vent installed is a top priority, strange that the cap I bought is not working as expected.

I did notice that the gas cap I use says "CAUTION: To Avoid Sudden Fuel Discharge, Rotate Cap One-Half Turn To Vent, After Hissing Stops, Continue Turning To Remove" which would seem somewhat odd given the description of the cap states it has both pressure and vacuum relief.
Old 05-24-2024, 09:49 AM
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I would guess the next question would be.... At what PSI does the cap Vent.... And at How many Inches of vacuum does the cap release.
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Old 05-24-2024, 10:59 AM
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Something that came up during my looking into the problem, should the carb bowl vent be capped or not? I have had people tell me it should be, but I have also read that it should not be, I believe 2 posts I had read even mentioned that with the carb bowl vent capped that it can cause problems starting when hot.

I'm debating drilling a hole through a spare gas cap I have, at least so that it is venting for now and then when I figure out a permanent solution putting the other cap back on. I am looking at removing the last 8" or so of the fuel filler where it is screwed to the bed side, this piece is metal, and figuring out a way to install a vent hose into that pipe. Not sure an NPT fitting will work, but that seems the simplest solution, however, the metal may be too thin to be able to thread the fitting into it. With a vent installed into that, I can put it back on the truck and route a hose up and then down again with a cheap fuel filter on the end to stop bugs and dirt from getting in. Might be the simplest solution if I can figure out how to get the hose secured to that last metal piece of the filler neck.
Old 05-25-2024, 05:18 AM
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The carb bowl line which I think you're talking about the tube that has a hose going to the canister that no longer is connected. That would be the hose that recirculates the gas fumes. I guess if the cap vented with a hole fixes your problem a good, vented cap should do the trick.
Old 05-25-2024, 05:31 AM
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Here's what I am looking at that wasn't capped originally, but then I was told to cap it, but I've also read not to cap it.



Here there is a picture and someone saying do not cap it. https://www.forabodiesonly.com/mopar...l-vent.334493/

I can't find it now, but I also read that with it capped it can cause issues starting when hot. But I've also seen where people say it's fine capped.

However, my carb has that solenoid (not connected to anything) so not sure if that impacts things.

I'm fairly sure that the tank needs a good vent, but I'm just also trying to determine whether this being capped is a problem.
Old 05-25-2024, 06:27 AM
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I guess uncap it and give it a try. May be causing the bowl not to vent properly
Old 05-25-2024, 02:11 PM
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Exactly the plan, I'll keep the cap in the truck in case it makes things worse though.
Old 05-27-2024, 07:27 AM
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Well, capped or no doesn't seem to make any noticeable difference, removed the cap and went for a drive in it yesterday with my youngest, it cut out half a mile from the house, started right back up, but I didn't want to risk breaking down with him so we drove about another mile, turned around and headed home. Put the cap back on the carb. Loosened the gas cap and you could hear the tank, what I assume, popping back into shape as I released the vacuum.

Left the cap loose, basically 1/4 turn from where it would click, just barely loose. Later in the day, went out on my own, a little over 5 miles to the gas station, filled up, came home, almost entirely uneventful.

Drove to the grocery store just now, almost entirely uneventful again, about a 20 mile round trip.

The only thing making these trips not 100% uneventful is that a couple times, the engine will just cut out and then immediately fire up again. If not for things like I see the volt meter drop to zero and my phone disconnect, I'd think it was a misfire with how quick it is.

Twice on the way to the grocery store, once headed home. I sat with it idling at the store for a minute and was jiggling the keys/ignition cylinder in case that was loose but nope. The only thing I've noticed is that it seems to do it when it's in 3rd with low rpm. Outside of that, it drives fine, no issues going up hill or picking up speed.
Old 05-28-2024, 04:39 AM
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The vacuum in the tank is definitely a problem. You can't suck fuel in a vacuum. As far as the engine cutting out and restarting that's a tuff one. Sounds like you're losing power based on your phone rebooting. Some of those older Dodges had issues with the amp/gauge and connections. I worked on a D300 that wouldn't start unless you wiggled the wires to the amp/gauge. Finally, we bypassed it and fixed it until we got another gauge and cleaned the connections good. .
Old 05-28-2024, 05:23 AM
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Originally Posted by Kuvasz101
The vacuum in the tank is definitely a problem.
Yep, that's gotta be top priority to get fixed. Especially as hearing the metal of the tank popping similar to a plastic bottle after you drink out of it, is clearly not good for the tank at all.

Originally Posted by Kuvasz101
As far as the engine cutting out and restarting that's a tuff one. Sounds like you're losing power based on your phone rebooting. Some of those older Dodges had issues with the amp/gauge and connections. I worked on a D300 that wouldn't start unless you wiggled the wires to the amp/gauge. Finally, we bypassed it and fixed it until we got another gauge and cleaned the connections good.
Yeah, it's strange, it does not seem to do it regularly either which makes figuring it out a little trickier. Driving you feel it cut out, it just fires right back up again. I may try to put some miles on the truck this week using it for some errands and just try to be very aware of things like the gear, throttle, RPM and so on when it cuts out. In the meantime I am going to check ignition components - lock cylinder, ballast resistor, coil and so on as well as check grounds. All the gauges read normal when it cuts and read the same when it comes back on, pressure is typically around 50psi, temp 180, voltage 15 or so.


Edited to add: Checking connections, found that I was able to get a solid "click" on 2 of the spark plug wires at the distributor cap and at the coil wire coming from the distributor. So, while they were on, they were not seated fully. Not sure yet if it will fix the problem, but certainly would not help things.

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Old 05-29-2024, 04:22 PM
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Looks like those loose connections might be it, got back from driving all over town earlier, the only time it cut out was at the end of my street. It's 1/2 mile, stop sign and a left turn, it cut out there, but I am not sure yet if that is due to it not being up to temp yet or exactly what, basically, stop then barely need to actually give it any throttle to pull out. Next time I drive I plan to give a little more gas as I pull away there and see if that does the trick.

Other than that, multiple stops in town, took it to a friend who owns a shop and had him go for a test drive, which involved a pretty steep hill, drove up the hill without any issue or needing to kick it down a gear. With the gas cap slightly loose zero issues starting either. Drove and pulled nicely in all situations.

Stopped in at O'Reilly for some supplies to change the rear diff fluid, no idea when it was last changed and so figure as part of the getting things done I will go ahead and do that.
Old 05-30-2024, 05:21 AM
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That gas tank under a vacuum and collapsing is a sure sign of a problem.
Old 05-30-2024, 06:21 AM
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Originally Posted by Kuvasz101
That gas tank under a vacuum and collapsing is a sure sign of a problem.
Agreed entirely, just trying to figure out the best solution currently. If the factory charcoal canisters were all still in place then I could look to use the original factory vent hose and go from there. But without that, I have to engineer a solution, the only thing I can come up with that does not involve dropping the tank, is removing this piece (assuming it is removable) of the filler neck and tapping a hole somewhere along the red line, then running a hose up from there in order for it to vent, or in this case, pull in air as fuel goes out.




I'm also trying to track down an oil leak, it's not the valve cover gaskets, but does appear to be coming from the top of the engine somewhere in the rear. Seems to mostly run down the drivers side of the bellhousing and get spread all over down there, I wiped off everything I could reach yesterday evening and am hoping to after a drive take a look and see if I can spot the culprit somewhere.
Old 05-30-2024, 06:37 AM
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Are you sure there is not a vent already built in to the tank and may just be plugged?
Check to see if a hose got pinched up on the top side of the fuel tank....
Some of those fuel tanks had a check valve up on top of the tank.... Or .... It should have a hose that goes to the charcoal canister / EVAP....?????
Anyways, Check to see if something got capped off or if a hose got somehow pinched some place...
Old 05-30-2024, 07:34 AM
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Originally Posted by RacerHog
Are you sure there is not a vent already built in to the tank and may just be plugged?
Check to see if a hose got pinched up on the top side of the fuel tank....
Some of those fuel tanks had a check valve up on top of the tank.... Or .... It should have a hose that goes to the charcoal canister / EVAP....?????
100% sure, this is the tank I have - https://www.holley.com/products/fuel...s/parts/19-592

Look closely at the pictures, there are 4 openings, pump, sending unit, filler hose and breather hose (the 90 degree one on top) and no other openings.

The original vent hose from the original factory tank, does still run along the frame rail up to the front where it should have gone into the charcoal canister, both ends are open as the canisters were removed by the previous owner.
Old 05-30-2024, 07:56 PM
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Seems to me the breather port should be connected to hose going to front and a charcoal canister connected. What is it connected to?
Old 05-31-2024, 08:26 AM
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The breather port goes up to the filler neck and is open there, in theory that should vent the tank, air should come in via the gas cap being vented for both vacuum and pressure, then go down the breather and into the tank preventing the vacuum. I wonder if there is a check valve on the tank itself, allowing air out, but not air in. I poked some weed whacker line down the breather hose just inside the gas cap and it is not blocked.

Old 05-31-2024, 12:39 PM
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The vent I believe you're talking about runs alongside the filler neck and dumps back into the opening where you fill it. That's used to fill it. Fuel pours in the neck and the displaced air goes up the smaller tube and into the fuel delevery neck. Yeah, with the cap on tightly not breathing that vent is useless.
Old 06-01-2024, 07:25 AM
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Ok... This is your problem.... The Tank Vent Hose... Needs to be vent to the atmosphere if your not going to route it to a canister...
My suggestion to most folks when they do this, is to install a hose and put a fuel filter on the end of it and hang it in the frame rail to the outside for venting... Mount toward the rear to keep any smell out of the cab and away from any ignition source...

That should fix that problem...
Old 06-02-2024, 02:56 PM
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Originally Posted by RacerHog
This is your problem.... The Tank Vent Hose... Needs to be vent to the atmosphere if your not going to route it to a canister...
Exactly.

Actually, right now there is no tank vent hose. I need to call Holley this coming week and ask where they suggest putting a vent hose as the tank does not even have a port for one that I could see. Once I figure out where to get the vent hose attached on the tank side of things, the other end will be fairly simple to achieve.


Drove the truck out to a cruise in last night, running nicely. Had a bit of an odd idle when I left, but I believe the choke had opened too soon, driving was fine, just idle was low and by the time I was home the idle was completely fine. Pretty sure I have put around 70-80 miles on the truck in the past week, it's been enjoyable driving around in it, windows down, ~75F temperature and no humidity. Perfect driving weather.
Old 06-03-2024, 10:02 AM
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Sounds like a plan….
once vented I think that should fix that issue..

good to here you are able to drive it a little and running the bugs out of it!!!
cheers..
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Old 06-06-2024, 11:44 AM
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Have not managed to get hold of someone at Holley yet, the "estimated wait time of 25 - 35 minutes" is not working out so well, I'll keep trying though. In the meantime have been cleaning various things up, maintenance etc.

Changed out the rear diff fluid, decided while it was apart to clean up and repaint the cover:



Removed and repainted the black behind the grill, masking the chrome was not fun, but really pleased with how this turned out.



Polished up the exhaust tips, also noticed that my painted cover almost matches the color of the shocks!



Polished the window vents with a little steel wool, these also came out great.



One of the pictures from the cruise in last Saturday.



Still have the fuel vent issue to fix, but also have to track down an oil leak from somewhere at the rear of the engine. I suspect it may be the rear main seal, pretty sure it is not the valve cover gaskets or the oil sender. One thing at a time and enjoying driving around in it while fixing things up.

Last edited by Abcdefghii; 06-06-2024 at 02:21 PM.
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Old 06-07-2024, 04:19 AM
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If you truly have a rear main leak, I'd try using an oil such as 5W30 Quaker State High Mileage Full Synthetic. This oil has seal swell in it. Oils like this won't fix a cracked or broken seal but it will swell a hardened seal that needs rejuvenating.
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Old 06-07-2024, 05:20 AM
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I am not sure yet if it is the rear main seal, the only other thing I can think of back there would be either the distributor O-ring or the intake manifold. I need to find someone with smaller hands who can help me clean up all the oil to make it easier to track down the source.
Old 06-13-2024, 08:36 AM
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Not much of any update, I had a complete nightmare trying to remove the chrome rails along the bed side to replace the vinyl tape on them. The drivers side came off easily, Philips screw and a nut, over to the passenger side and after going through this amount of tools...



Finally managed to remove the 2 nuts on the passenger side by carefully using a Dremel with a cut off wheel under the bed side to cut the nuts off. Thankfully, I did not need to remove the other 3 brackets holding the rail on as with the end removed they were able to just slide easily out.

Removing the old tape was not fun, tried a few solutions but nothing worked all that well and due to the size, getting anything to scrape it off was really tricky. The Dremel to the rescue again with a sanding drum, it marred up the surface a little behind the tape, but since I plan to replace the tape it's not a big deal. Currently trying to get as much shine back to the rails as I can before installing the new tape and putting back on the truck.



Next week taking it to a shop where they are going to help me try and determine where the oil leak is coming from and brain storm putting a vent on the tank.
Old 06-13-2024, 11:08 AM
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A little progress is good progress !!!!!! Cheers
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