Rebuilt carb and ran for a while but now nothing

Awesome site here, finally ran into a problem I cant solve by just searching now....

So my grandpa gave me his 1985 Dodge D250 truck [12X,*** miles] since he is no longer able to drive and I have been working on fixing it up as it has sat for a while. Its got a 360 5.9L v8 with a Rochester quadajet 4bbl carb.

We had the truck shipped down here and replaced the ignition control module and it has ran pretty well for a few months. I decided to rebuild the carb and purchased a rebuild kit from O'Reilly's. I thoroughly cleaned the carb just like i do with any other carbs I work on, checked and set the float level, and thoroughly cleaned all passages.

We put the carb back on the truck and it started up but ran really rough. We took it down the street and anytime you gave it gas it just wanted to die. we came back to it the next day and started it up and it would shake pretty bad and hesitate and die when you put it into gear. Now it wont even start, even with starting fluid.

Things that are new on the truck:
Ignition control module
ballast resistor
coil
distributor cap
sparkplugs and wires

The fuel pump is pumping and the plugs are getting spark. I can press down on the accelerator pump and see it squirting fuel into the intake.

Any ideas on what we need to check next? We cant even get it to pop off or anything with starting fluid.

It sounds like its flooded. If you end up taking the carb off again check to see if there are any cracks on the well plugs protruding from the bottom of the float bowl assembly. Not my pic but I JB Welded mine because I've read they're prone to cracking. Did a search and another thing that could cause it to flood would be if the needle and seat aren't sealing. In that case youd see a wet upper gasket. Welcome to RF.

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RonJon '06 said:

It sounds like its flooded. If you end up taking the carb off again check to see if there are any cracks on the well plugs protruding from the bottom of the float bowl assembly. Not my pic but I JB Welded mine because I've read they're prone to cracking. Did a search and another thing that could cause it to flood would be if the needle and seat aren't sealing. In that case youd see a wet upper gasket. Welcome to RF.

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Thanks for the reply, I did seal all the well plugs so shouldn't be any issues there. If it was flooding wouldn't you see gas pouring in or smell it? I will try cranking it a few times and see if the spark plugs are wet.

Yeah, if it's flooded it should smell like gas and if it's running rich it will backfire. Did you do the plugs, wires and cap earlier and not at the same time you did the carb? Just wondering if you should double check the firing order. If it was running before you rebuilt the carb and now it won't start I'd make sure you didn't miss something like a vacuum line. Also make sure the choke is working and that the secondaries aren't stuck open because that will cause it to bog down like you said. IDK I've always been able to get mine to at least start by pouring a little gas down the carb that's why I thought it might be flooded.

I've got the same carb and just rebuilt it and have done several adjustments on it so if you can get it to start maybe we can help you get it dialed in.

RonJon '06 said:

Yeah, if it's flooded it should smell like gas and if it's running rich it will backfire. Did you do the plugs, wires and cap earlier and not at the same time you did the carb? Just wondering if you should double check the firing order. If it was running before you rebuilt the carb and now it won't start I'd make sure you didn't miss something like a vacuum line. Also make sure the choke is working and that the secondaries aren't stuck open because that will cause it to bog down like you said. IDK I've always been able to get mine to at least start by pouring a little gas down the carb that's why I thought it might be flooded.

I've got the same carb and just rebuilt it and have done several adjustments on it so if you can get it to start maybe we can help you get it dialed in.

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When we got the truck I changed the oil, spark plugs, and plug wires. Also put a new ignition control module and coil on(the control module on it was shot and prevented it from starting). The truck ran alright around the neighborhood and would sit and idle just fine. Had to really pump the gas to get it to start if it sat for a while.

At this time, I decided to rebuild the carb and at the same time we replaced the valve cover gaskets and cleaned up the motor. I really went through the carb and replaced everything that came in the kit and sealed the well plugs with "Seal-All." Got the carb back on the truck and it would start but not idle to well and ran pretty rough. At this point we put a new ballast resistor on and tried a new ignition control module; still no luck. Replaced the distributor cap and still nothing. We checked all cylinders and they are getting spark and verified the firing order 2-3 times.

I have a boat with a 350 260hp v8 that has the same Quadrajet carb as this truck (the marine version). I put this carb on the truck just to see if we could get it to fire and make sure there isn't a problem with the wiring or anything. If I held the butterflies open the truck would sit there and idle. I opened up the top of the truck carb at this point to check the float level and it was just a little off, maybe a 1/32? Adjusted that and put the carb back on and still no luck.

The fuel filter in the carb is new and we pulled the gas inlet line off and cranked the truck. It seems to be getting a steady flow of gas.

Would you agree that it has been narrowed down to just a carb problem at this point? None of the carb faces seemed to be warped.

i would still recommend checking the fuel pressure with fuel pressure gauge to make sure you are getting enough especially if the fuel pump is stock. it could be worn out and not putting out enough pressure to keep the engine running properly.

When it was running did you do any adjustments on the carb? Curb idle, fast idle or air fuel ratio?

I'd say it sounds like the carb. Could be fuel pressure like Crazzy suggests especially if the other carb didnt want to idle either. A new fuel pump on these trucks are cheap and easy. If you pour about 1/4 cup of gas down the carb and hold the butterfly open it should fire up and run for at least a few seconds whether there's any fuel pressure or not.

BTW I have to pump mine like crazy too if it sits for more than a couple days.

I haven't done any adjustments to the carb at all.I figured I should get it running before I adjust anything.

I will probably just put a new fuel pump on it since they are fairly cheap like you said and just to offer some piece of mind that its not the original on there anymore!

Even after sealing the well plugs you still have to pump it?

you still may want to check the fuel pressure. i would also recommend installing a return less fuel filter. then even if you do have some fuel evaporate after shutting the engine off it should hold pressure long enough to top up the float bowl when needed and hopefully help the engine start better. this is part of the reason i like the holley carbs so much. got such a large float bowl they don't really have to worry about fuel evaporating out of the float bowl

Yep, I've had to pump it 30-40 times after not driving it for a few weeks lol.

My '85 sat for a long time before I got it and I replaced the fuel pump even though the old one seemed fine

Thanks for the input, Ill replace the fuel pump and see what happens. Any reason someone would add an electric pump and still keep the mechanical pump? My grandpa said he brought it in for repairs a long time ago and he believes they added an electric pump inline with the mechanical. I dont hear a pump kick on when I turn the key so I still need to see if there really is one.

Any thing special to look into for the return less fuel filter? I assume I can just buy an inline fuel filter for a big block and cap off the return line?

you can just cap off the return line on a normal filter but usually a return less fuel filter looks a bit nicer.

should be no need for a electric fuel pump but some did come with one from the dealers but i forget the reason for it.

Alright so just got a new mechanical fuel pump on and the truck started!
Replaced all the fuel lines in the engine bay, put a return-less filter on and capped the return line to the tank. Also put a new filter in the carb.

The truck starts and now has a rough idle. Also, when we go to put it into gear, it stumbles really bad and dies. Any idea what may be causing this now? What adjustments should I look into for the carb?

The first thing you want to adjust is the air/fuel ratio. There are two adjustment screws facing forward on the lower front of the carb. Mine were covered by the factory plugs and they were not easy to remove. Make sure the engine is idling and up to temp and turn one of the screws counter clockwise (out) until the rpms increase. Keep turning until the rpms decrease then turn it back clockwise until the rpms increase again. You want it at the point where the rpms are the highest. Adjust one then move on to the other one.

Once you've adjusted the air/fuel ratio you can adjust the curb idle. There is a screw on the driver's side of the carb by the throttle linkage.

Lastly there is a fast idle screw on the passenger's side of the carb below the choke spring housing which needs to be adjusted while the engine is still cold. The fast idle should kick down 2-3 times as the engine warms up.

Make sure the choke is working by lifting off the air cleaner cover. If the engine is shut off while its warm the butterfly on the choke should be all the way open. When you go to start the truck (cold) the butterfly should close when you depress the accelerator pedal once all the way to the floor.

There's a guy on YouTube called WhoSaidTyler, he has several videos that will walk you through the whole process. Glad to hear you got it started.

So I tried adjusting the air/fuel mixture and was having a hard time hearing a difference in the RPMs so I hooked up a vacuum gauge to the port by each adjusting screw. As I was adjusting the drivers side, there was no real change in the vacuum and there was no vacuum at all on the passenger side. Would this indicate that there is a clogged passage in the carb or another issue?

I got the truck to run a little better, but it is still having a hard time idling until it gets warmed up, and it still dies when we put it into gear.

that almost sounds normal. almost every carbed engine out there will not run great until the carb has hit full operating temp which usually take about 15 or more minutes. even after 5 minutes of running my truck will still want to stall when in gear until it is at operating temp. just the colder it is the easier it is to stall

crazzywolfie said:

that almost sounds normal. almost every carbed engine out there will not run great until the carb has hit full operating temp which usually take about 15 or more minutes. even after 5 minutes of running my truck will still want to stall when in gear until it is at operating temp. just the colder it is the easier it is to stall

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But the thing is is that it never did this. I use to be able to go out to the truck, start it right up, and immediately put it into gear and drive it.
Now even after sitting for 20 minutes, it dies when I try to put it into gear and drive off.

I'd pull the vacuum hose off of the choke pull off and see what kind of vacuum you have at idle, that should be manifold vacuum. I was reading that the EGR can cause stumbling off idle and that it has its own specific ported vacuum source which I believe is on the fromt driver's side of the carb. Any chance the vacuum lines got mixed up or something's not connected? Manifold vacuum at idle should be 17-21mmHg.