[Slater2028]

Hi all,

I am new to this forum as I purchased a 1981 dodge d150 custom a few weeks ago. First thing I did was to have the transmission professionaly rebuilt as it was obviously damaged. I changed the oil, the air filter. It has no power. On the highway, it cannot keep its speed when going up an incline. Not even a big one. It accelerates from 0 to 60 in the longest time. I did a couple sea foam treatment in the gas tank and also directly in the carb. Now it performs slightly better but still the power is not what it is supposed to be. I am breaking my head over this. I am not a mechanic but I am able to do some work. I have searched and read this forum a lot in hopes to find the issue. I understand a timing issue could explain my poor mileage and power, but I don't hear any pinging. As far as I'm concerned, the engine sounds nice. The only thing I can say about this truck is that the owner before me has put a one way valve on the line bringing fuel to the carburetor. Today I'm gonna change the fuel filter as it seems a little dirty. From there, I don't know. Anybody has had this problem too??

 

[WinterTurtle]

Fuel filter always a good call.

Could be a lot of things - but if the PO installed a check valve in the fuel path that sounds like a clue. Your mechanical fuel pump should act as a check valve anyway so I have no idea what the person was thinking.

What kind of carburetor do you have? If it's an old BBD or something it could just be somewhat cloggy. Especially if it has sit for a while.

Also never hurts to do the cheap basic tune up items to be safe. Plugs and wires + cap and rotor to make sure good spark is getting there.

Kudos for taking on a project out of your traditional comfort zone. 95% of mechanic work is having the cahones to start the process and tell yourself you can. In reality none of it is all that hard - just challenge yourself to be analytical. Always check the basics first while being conscious that everything in the system is related. Anywho - good on ya new chum.

 

[Slater2028]

Fuel filter always a good call.

Could be a lot of things - but if the PO installed a check valve in the fuel path that sounds like a clue. Your mechanical fuel pump should act as a check valve anyway so I have no idea what the person was thinking.

What kind of carburetor do you have? If it's an old BBD or something it could just be somewhat cloggy. Especially if it has sit for a while.

Also never hurts to do the cheap basic tune up items to be safe. Plugs and wires + cap and rotor to make sure good spark is getting there.

Kudos for taking on a project out of your traditional comfort zone. 95% of mechanic work is having the cahones to start the process and tell yourself you can. In reality none of it is all that hard - just challenge yourself to be analytical. Always check the basics first while being conscious that everything in the system is related. Anywho - good on ya new chum.

Thanks for the comments!
I think I'll try to remove the one way valve to see how it behaves.

The carburetor is a Rochester Quadrajet. For some reason, the carb that's on it is a 1984 while the truck is a 1981. I looked up the numbers online.

I like your suggestion on the plugs and wires, cap, rotor. Even though the wires don't look old, it's cheap and I could eliminate that from the process!! haha

Have a good one

 

[WinterTurtle]

Ooooo Q-jet awesome! I do love those. Been a good while though. They're great units though metering rods and such are getting rare.

Take a few minutes if this is new - and read up on potting and plugging the factory Welch plugs in the bottom. I dont think I've heard of it causing running performance issues but still worth the read... https://www.hotrod.com/articles/hppp-1107-home-remedy-quadrajet-carburetor/

General thought - check the pulloff valve thing and make sure it's hooked up and actuating with vacuum.

Here's a chunk of bad performance discussion:

Easy things first, make sure that the secondary metering rods are still on the hanger. Next, take a piece of vacuum hose and check the air valve pulloff diaphragm - they're often broken. This is mounted on the front, passenger side.

 

[Slater2028]

I checked some of the vacuum hoses today. two outlets are capped on the carburetor but the caps were broken and sipping a bit of air. changed both caps, now it is a bit better. I'm wondering about the timing. I might check that next.

Other than that, something got me thinking. I'm not sure if the engine is vibrating normally at idle, or excessively. It's my first V8 truck so I have nothing to compare it to. It sounds good at idle, but is shaking like a harley. I'm just thinking about this now. maybe it's supposed to not shake at all.

I plan on ordering a rebuild kit for the carburetor from Cliff's performance. Then I'll tinker that when the weather gets warmer. lol

 

[WinterTurtle]

Yeah 318s should run like sewing machines. Known to be very smooth with stock cams. I can leave a can soda on the air cleaner and it not move.

Let it run and remove the spark plug wires one at a time. Removing a wire should cause the motor to run crappier. If one makes no difference then you have a misfire on that cylinder somehow. A nice easy check and ypu can take next steps if one appears to be an issue.

Rebuilding and setting up the carb will no doubt help. Get yourself a tach (a buddy in the cab of the truck has one works) and adjust it by a good procedure.

Id recommend tapping and potting like in the link if you're already doing a rebuild - but if it looks good its your call there. Likely not the core issue you're facing.

Getting a timing light to check is easy insurance. Make sure and remove then cap the vacuum advance port before checking or setting.

Are you able to post pictures? I am curious to see a whole engine bay shot - and a shot of one of the spark plugs before cleaning. The color and all are good clues of how a motor is running.

 

[WinterTurtle]

Another thought - what is your voltage at idle and is it stable?

How about at 2000rpm?

Mopar ignition HATES low or goofy voltage.

 

[Slater2028]

So yesterday I did remove the spark plug wire one at a time. Cylinder #8 is the guilty one. I was all happy and went to get a new spark plug but the issue remained. lol Spark plug wire is good. I thought the spark plug that was in it would be all wet but it isn't. It looks nice. i attached a picture. i stopped by a mechanic shop and the guy suggest i do a compression test. he thinks timing is not an issue. I want to remove the valve cover to see if there is anything obvious.

I checked the spark plug wires to see if they are connected properly on the cap. they are. Then engine has 60K miles on it. So I would be surprised if it is worn out that much.

What could be specific to cylinder #8?

 

[Slater2028]

Here is the engine bay.

 

[WinterTurtle]

Oh wow clean enough to eat off of! Yes I agree the plug looks pretty normal which is interesting.

A compression test would be best. Local parts houses sometimes do them as rental tools. If you don't have one available then you can pull the plug and put your finger over the hole and crank. It should blow your fingertip off repeatedly as it goes through the compression stroke. You can also compare to an in theory 'good' cylinder to compare.

Its not as if its super common but a broken ring or junk in the cylinder could cause this. Do you know if your oil fouls quickly after a change? Thats commonly associated with a cylinder that can't hold pressure. For the same reason you have a fully cylinder of blow by so engine running and oil cap removed of you have a steady stream of pressure or smoke exiting the oil fill thats another indicator. Some blow by is normal on an old engine but if its chugging then =(

 

[WinterTurtle]

You can also pull the plug then reconnect the wore and hold the plug threads to a bolt on the motor (grounding) and crank to be sure there is actual happy blue spark on the plug. 'Seeing is believing' so to speak and 'out of box failure' parts are more common today than ever before...

 

[Slater2028]

Yes the oil is dirty but not discusting yet. I changed it when I got the truck so it's been about 2000 km. The oil is now dirty but I assumed it's because I put seafoam in the crankcase. The next time I change the oil I'll keep an eye on that. I'm crossing my fingers that this will be a quick fix as I do not want to rebuild the engine at this point. That's something I plan to do later on when I'll have time and a new garage. lol Hopefully it's a ring or junk like you said and it can be fixed.

I appreciate your feedback!

 

[WinterTurtle]

Well... hopefully not a ring cuz that would be bottom end repair that usually means you should rebuild. It could also be a stuck or bad lifter or something... if you find its not pushing compression then the next check id recommend would be under the valve cover and watching to see of your rockers are actuating properly and valve is returning properly.

I hope on your behalf that it turns out to be minor. The 318 is super super reliable so hopefully. And a stuck valve can commonly be improved of not fixed.

Just a few more paces down the road.

 

[cribbs74]

I know your mechanic said the timing was probably fine, but it really sounds as if it’s too retarded. It’s super easy to check if you have a timing light and if you don’t, although not correct, you can just adjust it until it pings on acceleration and then just back it off until it stops.

Just loosen the distributor just enough to where it can move by hand and go for a drive. Make adjustments along the way until it’s where you like it and then lock it down.

Keep in mind you have an 80’s 318 with low (from factory) compression and smog heads and questionable lean burn ignition. You are working with considerably less than 200 net hp to start with and trying to pull around close to 4000lbs. Depending on gearing and I am assuming an auto trans you really don’t have much power to the wheels. It was never a stump puller even when new.

However, it should be able to get out of it‘s own way.

Ron

 

[44MagLeo]

Nice looking truck. I like the olde vehicles myself. Easier for an old fart like me to understand.
I agree with others that reccomend a tune up. Plugs, wires, cap and rotor are all a good idea.
The SeaFoam is a good product. It works a bit slower than others but is less apt to hurt things.
Doing a compression check isn't hard to do. A lot of parts stores have loaner tools, Around me adavanced auto does. They charge a deposit that covers the cost of the tool if you decide to keep it. If you want to buy one they can be found less expensive other places.
The compression test can tell you alot about your engine. Do it first on cold dry engine. Then squirt a bit of oil in each cylinder before a second test. If the difference from before to after don't change that indicates the valves are sealing. It it goes up up after it could be rings. There are other tests that can be done that can help verify what the compression tests indicate. Leak down testing is one, a vacuum gauge test is another.
If it sat very long before you bought it, clogged fuel system parts is likely. Sticky valves can also happen.
Leo

 

[guyonearth]

Are you sure the catalyst isn't plugged? Sure sounds like it. What's all that wiring running all over the place?

 

[Slater2028]

I know your mechanic said the timing was probably fine, but it really sounds as if it’s too retarded. It’s super easy to check if you have a timing light and if you don’t, although not correct, you can just adjust it until it pings on acceleration and then just back it off until it stops.

Just loosen the distributor just enough to where it can move by hand and go for a drive. Make adjustments along the way until it’s where you like it and then lock it down.

Keep in mind you have an 80’s 318 with low (from factory) compression and smog heads and questionable lean burn ignition. You are working with considerably less than 200 net hp to start with and trying to pull around close to 4000lbs. Depending on gearing and I am assuming an auto trans you really don’t have much power to the wheels. It was never a stump puller even when new.

However, it should be able to get out of it‘s own way.

Ron

So I did check the timing with a light. I couldn't see the line on the balancer, so it was way off. I had to go back to the mechanic so I also asked him to check it, to confirm if I was doing it right. He did see the line. It was way advanced, so he put it back to 10 degrees, where it is supposed to be. But I didn't notice anything while driving it after.

Did a compression test on cylinder # 8, very low compression. The guy tinks it might be a burnt valve.

I understand that these engine don't make a lot of power to begin with. I'm comparing it to my Sprinter 2500 that produces similar power. 160 hp and about 260 ft-lbs. The D150 was supposed to be 175 hp and 240 ft-lbs. My sprinter really moves compared to the truck. it's seven speeds vs 3 speeds but even at highway speeds, my sprinter moves a lot more.

Looks like the head will have to come off.

 

[Slater2028]

Are you sure the catalyst isn't plugged? Sure sounds like it. What's all that wiring running all over the place?

I think there is no cat on this truck. The sticker under the hood that says what equipment in on the truck mentinos cat converter delete. The exhaust is pretty much straight pipe. I'll look properly to be sure.

The wiring looks silly right? The is quite a few plugs lying around. I'll take some pictures.

 

[44MagLeo]

The weight of your sprinter and the gearing of the transmission as well as final drive all make a difference in the acceleration. The 7 speeds of the sprinter help a llot.
I had a 94 ram 1500 with the 318 with the 4 speed overdrive auto. It did very well on acceleration. From the sgart or passing.
One bad cylinder will make it run rough but it shouldn't have as great an impact as what you are talking about.
When I was younger my brother had a Pontiac Catalina, with a 389 It had about the same carb as you have, I don't recall the year but it had a burnt exhaust valve on one cylinder. It ran rough. My brother just removed the plug wire for that cylinder. It ran a bit smoother that way and had plenty of power.
I thionk you may have more issues than jst one bad cylinder.
I might look around to your local auto salvage yard for another engine.
It will be cheaper than a rebuild. Around here iat te You Pull It yards an engine costs around $150. More if they pull it.
A 318 from most any years should swap in easily. Different years used different sensors so transfer all your sensors from the current engine to the replacement.
If the enfgine come from a later vehicle and has fuel injectiuon you need to swap your intake and carbs to the replacement as well.
Leo

 

[guyonearth]

My brother just removed the plug wire for that cylinder. It ran a bit smoother that way and had plenty of power.

That is the craziest thing I've ever heard.