Need some advice about problem when I get on the gas

[andyblack]

I'm having a problem that I can't figure out and I was hoping some of you gurus might have some suggestions for me.

I have an '85 truck with a 305, stock quadrajet, HEI, mechanical fuel pump, etc. The other day I noticed that when I went up a hill and had to get on the gas, the engine started cutting out a little. The next day it would only go about 50. Also then it started running on only 7 cylinders, so I put in some new plugs and wires and then it ran great until it got up to about 45. Then it would cut out. Then it would only go 40, 35, etc. until it now it cuts off when I get on the gas every time basically. What gives? Someone suggested the little plunger thing that's in the front of the carb (I can't remember the name of it. Power piston?), but it seems to be springing up and down just fine. I've had the ignition module in the distributor go out before, but it didn't do exactly like it is now. I did notice that when I put the new plug wires on, some of the contacts felt loose on the cap. I didn't take the cap off to inspect the rotor, however, I don't believe it's a spark issue because I'm not smelling any raw fuel when this is going on, and like I said, it runs great when it's idling and when you first start going. I put a new fuel pump on a couple of years ago. Like I said, it runs great until I get to a certain speed, then it starts cutting out and dies unless I get off the gas. This happens in any gear and it seems to be getting progressively worse. I can't drive it until I get this problem fixed. What do you fellas think is the culprit?

 

[41bigdawg]

I am just guessing here but have you changed the fuel filter lately? I have seen that cause some strange things in the past. Just an idea.

 

[andyblack]

I am just guessing here but have you changed the fuel filter lately? I have seen that cause some strange things in the past. Just an idea.

I don't think it even has a fuel filter. Or if it does, I haven't seen one. I think there may be a small one up there by the carb, but I haven't seen one on the frame rail like most later model trucks have. Where would the fuel filter be on these old trucks?

 

[41bigdawg]

On a Quadrajet Carb the fuel filter is in the carb right behind where the fuel line enters. Just use a line wrench to remove the fuel line and the filter is right there. Make sure that the spring is present as this keeps the filter tight to the fuel line, otherwise you wont be filtering anything. Hope that helps.

 

[andyblack]

Yeah okay thanks. I'll look at that. What do I need to do to keep gas from spilling out?

 

[41bigdawg]

You will get a little spillage from the line and the carb but shouldn't be excessive. I usually just put a rag underneith to soak it up. There won't be any pressure since it isn't running. Make sure that you soak up any residual and I usually wait a few minutes to let the fumes flash off before I start it up.

 

[dyeager535]

Those filters bypass when plugged. You'll see that it's spring loaded when you remove it. Be careful undoing that nut, use tubing wrenches. I also would suggest loosening the metal line at the *fuel pump* first. It seems to help prevent the line from twisting as you loosen it at the carb...sometimes the line wants to turn with the nut at the carb, if it can't turn freely, it will kink, and last I knew, those lines are impossible to get.

Here's what I'd do. Get the truck to repeat the problem. Shut it off while it's doing it, and take it out of gear quickly (so you don't keep spinning the cam which will work the fuel pump). Pull over, pop the air cleaner off, and manipulate the throttle, watching for fuel to squirt into the primary venturi's. If fuel squirts, there is some in the throttle body. If not, then you obviously have an issue with fuel getting into the float bowl for whatever reason.

I had a similar problem. Under heavy throttle, the truck would start bucking like it was out of fuel. If the load on the engine was decreased enough, it would run fine. Turned out to be a stuck float. Simple rebuild on the q-jets (short of bushing the primary throttle shaft) and pretty cheap, kits were ~$25 last I checked.

 

[Ol.Luce]

Just watch for extra pieces when you're done.... I'm stilling for a place to put two screws..

 

[andyblack]

I changed the fuel filter yesterday. I saw that line start to twist a little but was able to back off and not break it and then straighten it out before it was too late. I used a 5/8" line wrench and still ended up messing the nut up some and having to use a pair of vise grips to get it to start loosening. I was like "give me a break." I got it in there though but I somehow doubt that fixed it. Looks like some carb work is in my future.

I didn't get to test drive it because my dumb butt decided to step on the wheel to get up to the carb (I'm not very tall) and broke the valve stem off with my foot. So I had a flat front tire within 10 seconds. What next? I just can't believe I didn't break that fuel line or some vacuum hoses or something like that. In case yall haven't caught on yet, I'm not too much of a mechanic at all.

 

[dyeager535]

Trust me, the carb lines get pretty much everyone. They do a real good job of binding up after sitting for 20+ years. At least you got it out without completely ruining it, or anything else that would require a lot of effort to fix. It's one of the reasons I don't like messing with the carb filters. But *if* you've got to rebuild it, needed to get the line loose anyway.

 

[andyblack]

I got my tire fixed and put back on yesterday. I put some Gumout carb cleaner in the tank and drove around real slow (30 mph) for a while, hoping that would clear it up. No such luck. Looks like the carb will be coming off soon. The top half at least. Maybe I won't tear anything up.

 

[wallerus]

I got my tire fixed and put back on yesterday. I put some Gumout carb cleaner in the tank and drove around real slow (30 mph) for a while, hoping that would clear it up. No such luck. Looks like the carb will be coming off soon. The top half at least. Maybe I won't tear anything up.

Before you jump off the carb bridge there are other things to check. While most people that I have met hate Quadrajets, they are a very forgiving carb. Unlike a holley where if you don't eat the right breakfast you have to rebuild that POS. 9 times out of 10 the problem is not in the carb unless you reallllly have some skank fuel. The issue sounds like you are running out of fuel. If the float was stuck it more than likely wouldn't run at all. Pull the fuel line off the carb and attach a piece of rubber hose to it, at least a foot long. put the hose in a bucket, mason jar, what ever, and crank the engine for 15 seconds. Should fill up about a quart. If not, your problem is between the tank and the carb.

Could be, but not limited to, bad fuel pump, extra filter in the line plugged, kinked fuel line, bad screen on the pick up tube in the tank.

Check all items dealing with fuel flow and pressure before you pull the Qjet or you'll just piss yourself off if it doesn't work. The next thing you know, out comes 44.

 

[andyblack]

Hey thanks for the good advice. I know it's always best to look at the simplest things first and go from there. Troubleshooting 101. I should know that since I troubleshoot electronics at work all day.

Anyway, I thought maybe the fuel pump was the culprit so I took a good look at it and found the big hose was kinked. Straightening it didn't help but I did notice the small hose seemed loose so I started the engine and watched that hose and I could see gas dripping out pretty bad even at idle. I got me a new hose but it would only get tight enough when I ditched the quick release constant tension style clip that was came on there and used a small hose clamp. Went out for a test drive and got on the gas and now all is well. Okay that problem is fixed anyway.

So thanks for all the input and advice guys. Sometimes just asking questions and reading folks' input is what it takes to get me thinking so I can at least go in the right direction. CK5 is a great place to start.