Loss of power

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Loss of power

Post by WyldeBill66 on Thu Apr 04, 2013 11:18 pm

So my 75 Chevelle is acting up again. I have found what looks like it may be varnish in the fuel lines, but it isn't showing up in the fuel filter I installed. I blew it out of the rubber lines that come out of the hard line. If I am sitting there in neutral and I rev the motor up and hold it up over 4,000 RPM's, it runs no problem. Once I get on the freeway and get to about 60MPH and up, it starts losing power. I don't know if it's a fuel starvation issue, or if there is an issue with the coil. What do you think? I took the fuel line off and turned on the electric fuel pump and it seemed to pump a lot of fuel out. Plenty to supply the motor in my opinion. I don't know the condition of the coil since I didn't put it in. Only owned the car since September.

Any thoughts on which is more likely?

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Re: Loss of power

Post by 2fat2fly on Fri Apr 05, 2013 12:43 am

WyldeBill66 wrote:So my 75 Chevelle is acting up again. I have found what looks like it may be varnish in the fuel lines, but it isn't showing up in the fuel filter I installed. I blew it out of the rubber lines that come out of the hard line. If I am sitting there in neutral and I rev the motor up and hold it up over 4,000 RPM's, it runs no problem. Once I get on the freeway and get to about 60MPH and up, it starts losing power. I don't know if it's a fuel starvation issue, or if there is an issue with the coil. What do you think? I took the fuel line off and turned on the electric fuel pump and it seemed to pump a lot of fuel out. Plenty to supply the motor in my opinion. I don't know the condition of the coil since I didn't put it in. Only owned the car since September.

Any thoughts on which is more likely?

Just a thought I have seen a good looking set of plug wires be bad and to listen to it run you'd think hey no miss whats the deal.
It was a 73 Buick estate wagon with the 455 and it always ran strong so on one our trips south over the grapevine this thing would not pull or do any better than 60 mph with my foot on the floor, (ran smooth).
I got home and did the normal searches and found that the wires were the culprit, could be a cheap fix !
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Re: Loss of power

Post by WyldeBill66 on Fri Apr 05, 2013 12:50 am

It doesn't run smooth at all once it starts losing power. It's feels and sounds like it's either not getting fuel or enough spark. Not sure which. That's what's driving me nuts. It was doing this when I first bought it, then I got it running pretty good. I tried adjsting the carb to make it a little richer, and it started running bad again. I set it back to where it was before, but it's still running bad at highway speeds.


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Re: Loss of power

Post by Limey SE on Fri Apr 05, 2013 1:12 am

Do You know how much fuel pressure you have? It could be a pump going bad or the accelerator pump in the carb could have small cracks in the rubber, if its been sitting for awhile. When you mash it your not getting enough fuel in through the carb. How new are the plug wires? When you mash it you are putting a load on the ignition system. Is the centrifical advance working? Can you hook up a timing light and check to see if it is advancing when you give it gas? you should have full advance in by about 3,000 rpm, keep it arround 36 degrees. these are 3 things I checked when my car was doing the same thing. It turned out to be the advance was messed up. Hope this helps
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Re: Loss of power

Post by WyldeBill66 on Fri Apr 05, 2013 1:19 am

not sure of the fuel pressure. I have to get a pressure gauge. The carb is pretty new as well as the pump. the plug wire are definitely suspect, but I don't have much money, so I'm trying not to just change everything since I don't have the money. I'm going to take a look at the advance this weekend. I was thinking the same thing. I can't check the timing accurately. I have a timing light, but the mark on the balancer isn't even close to where the timing marks are. It's an 87 style crate motor, and I don't know if the balancer is different or if the outer ring has moved. I'll check to see if it moves when I rev the motor.

Thank you for the tips Limey.

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Re: Loss of power

Post by fishhead on Fri Apr 05, 2013 1:37 am

Have you checked the timing?Is it the original distributor?Have you inspected/replaced your spark plugs lately?Have you checked your vacuum advance canister with a gauge? What condition is the vacuum hose in? Have you checked your cylinder pressure with a compression gauge?In a worst case it could be worn out valvesprings.Sometimes catalytic converters clog up after mega miles.Also,your distributor advance weights could be sticking and thats an easy fix with a little cleanup and light lubricant.Sorry to throw all that out there but maybe it will help you find the problem.Also,check your "butterfly valves to be sure they are opening all the way at WOT,I had a scare years ago and it was just a linkage rod on the carb choke came loose and was cutting off the air supply.

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Re: Loss of power

Post by WyldeBill66 on Fri Apr 05, 2013 1:41 am

I have a lot to check out this weekend. It has an Edelbrock carb, and the motor is practically brand new. The wires are a funky looking set that the previous owner threw on there. The electric choke isn't hooked up, so maybe that is the issue. I just have to run the power wire and ground it properly. Maybe it just can't breathe...so many things to check. Isn't this a great hobby...Good thing I don't have any hair to pull out...

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Re: Loss of power

Post by dynchel on Fri Apr 05, 2013 6:45 am

Check the condition of any and all rubber fuel lines. Any cracks will suck air, or they could be collapsing. I once had a similar problem on a s15 truck, it would run OK then it would lose power replacing the rubber hoses fixed it. I would definitely replace the line over the rear end. Good luck happy bowtie
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Re: Loss of power

Post by Tom77 on Fri Apr 05, 2013 10:49 am

One more item for your to do list. In 75 they started to put cats on these. Does it still have one. I would check for obstructions or dents in the exhaust. That will definatly cause the problem you are describing also.
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Re: Loss of power

Post by 77mali on Fri Apr 05, 2013 1:07 pm

You can take your Dist out & have it tested (maybe @ autozone or another chain) that's not a big deal & you can eliminate the coil as the culprit.

The carb might not be the problem. You might be loosing air flow (if you have the original motor to the car) because the air intake manifold's cross over chamber is gummed up with carbon deposits. I would try running some Seafoam (spray version) first through a vacuum line to clean out the carb, get it into the air system & hopefully eliminate that. Go for a 20 minute test drive afterwards & keep it below the rpm range you're having trouble with to let the cleaner go to work. It may be that it will run rougher for a while because of all the crud that may be accumulated - let that settle out as much as possible before you head out.

Make sure to follow the directions on the can, too much cleaner isn't good either- it may take a couple of applications.


Just a thought too- if the engine is able to hold 4000 in neutral could it be your trans or converter? If the other stuff checks out- including good exhaust flow/air fuel mix/dist coil/spark, etc. You may at least want to check.
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Re: Loss of power

Post by pila on Fri Apr 05, 2013 2:25 pm

Timing is not the problem if it's running rough. The engine can run smooth even if the timing is off some. Your problem could be a number of other things. If you have a Q-jet carb, did you check the filter inside of the gas line inlet fitting on the carb ? To check it, you have to hold the inlet fitting with a wrench, while removing the gas line, then remove the fitting and the filter, which has a spring behind it. If you can't blow through the fliter, toss it.....

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Re: Loss of power

Post by WyldeBill66 on Fri Apr 05, 2013 2:26 pm

All the fuel lines I can see look good, but I will have to drop the tank to see the connection at the tank. It isn't the original engine. It's an 87 style 350 with a Holley intake manifold and Edelbrock carb. The exhaust is headers with Flowmaster mufflers. I'll have to check with autozone to see if they do distributor testing here.

I'm definitely going to check out the choke as someone suggested. It might be getting sucked closed since the electric choke isn't hooked up.

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Re: Loss of power

Post by pila on Fri Apr 05, 2013 2:44 pm

If the choke isn't hooked up, do you have it secured in the open position ?
No big deal to hook up the electric choke. You can tap into one of the wiper wires for power to the choke. It would be the power wire, which is only powered when the ignition is on.

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Re: Loss of power

Post by Fishgrinder on Fri Apr 05, 2013 4:23 pm

Have you checked that there isn't any debris caught between the needle and seat, and that the float level is correct?

I would expect the carburetor to flood and lots of smoke out back, if this was the case, but perhaps it's an "in between" situation. When you are reving it consumes enough fuel and the fuel level is ok. When you are cruising at the higway at lower rpms the fuel level rises and makes the mixture way too rich.

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Re: Loss of power

Post by WyldeBill66 on Sat Apr 06, 2013 12:42 am

I don't have the choke secured open, that's what I'm thinking it is now. I'll see tomorrow.

I checked the floats, and they are set correctly.

I'll let everyone know what I find out tomorrow when I take a look at it.


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Re: Loss of power

Post by WyldeBill66 on Sun Apr 14, 2013 2:08 pm

Just to let everyone know, since I forgot to come back and post an update, the car is running good now. I put the sta-bil in the tank and hooked up the choke. I think it was a combo of the two issues causing the problem. The choke was staying closed too much and not allowing enough air in, and the bit of stuff in the tank added to it. I will keep using the sta-bil each time I put in gas until the bottle is gone, and hopefully that will solve the problem permanently. I hope I don't have to drop the tank and have it cleaned. No funds for that.

Thank you to everyone that gave me suggestions and offered help. you guys are great.

Bill

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Re: Loss of power

Post by Limey SE on Sun Apr 14, 2013 2:32 pm

I would use sea foam before stabil over and over Stabil is more for storing a vehicle I don't know what it would do to a carb by constantly using it ??
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Re: Loss of power

Post by WyldeBill66 on Sun Apr 14, 2013 3:09 pm

I'll check into that Limey. Thank you. It does say it won't hurt anything by using too much though.


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Re: Loss of power

Post by Mcarlo77 on Sun Apr 14, 2013 5:04 pm

Are you running ethanol blend in your car out there in CA? And, is this your daily driver?
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Re: Loss of power

Post by pila on Sun Apr 14, 2013 6:24 pm

Stabil isn't a cleaner, like Seafoam. It's mostly for keeping the ethanol suspended so it doesn't settle in and form gunk in the system.

There have been numerous additives for cleaning fuel systems over the years, but Seafoam seems to be better than most these days.

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Re: Loss of power

Post by WyldeBill66 on Sun Apr 14, 2013 6:49 pm

Just regular gas, which I believe they put a bit of ethanol into it here, just don't know how much. I'll just run it like this for now and see how it does.
I read that the seafoam can break stuff loose and actually make it worse if there is a lot of it.

Thank you for all the info though. I'll keep it in mind if it starts acting up again.

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Re: Loss of power

Post by Limey SE on Sun Apr 14, 2013 7:53 pm

Limey SE wrote:I would use sea foam before stabil over and over Stabil is more for storing a vehicle I don't know what it would do to a carb by constantly using it ??




Safely helps quiet noisy lifters, helps remove fuel deposits and oil residue, helps smooth rough idle. For Carburetors or Fuel Injected Gasoline Engines Autos Trucks Tractors Motorcycles Marine Small Engines Industrial Engines Great for Diesel Engines Too!

SEA FOAM Motor Treatment is a petroleum based product that helps clean internal fuel and oil system components. SEA FOAM is an EPA-registered product, and will not harm engine components, seals, gaskets, catalytic converters or oxygen sensors.

SEA FOAM helps liquefy gum and varnish deposits when added to fuels or oils. Mechanics have used Sea Foam for many things over the years including cleaning fuel injectors when using their professional injector cleaning machines also used to clean air induction systems and Throttle Bodies. When Using Sea Foam Motor Treatment to clean Air induction systems and Throttle Bodies the use of an S tool attachment is necessary to soak down the Throttle Body. If you do not have an S Tool at your disposal Sea Foam Spray should be used. Next a nylon brush is used to clean throttle plates and throttle body housing. This is only a few examples why Sea Foam has been so popular with professional mechanics for over 70 years.

As a fuel system additive, Sea Foam helps, clean carburetor jets, clean passageways, clean fuel injectors, clean deposits, stabilize fuel for up to 2 years, control moisture and adds lubricity to fuel.

As an oil system additive, Sea Foam helps prevent and clean oil residue deposits.
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Re: Loss of power

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