Engine Running Poorly

[goodnigh]

The last few days the car has been running poorly.

Long story short, we went through the ignition

system and could not find a problem. No matter

where we set the timing, the engine ran rough. All

wiring is intact. Bought new electronic points to replace

the "suspect" set. No change. So we started looking

at fuel delivery. Fortunately my Holley has fuel level

windows. With the windows at half (which is good) we

started the engine. The fuel level dropped and did not

return. The car would idle but if you tried to drive it....

My mechanic thinks it is the fuel pump. Could be a

clogged filter. A new SS 3/8 inch fuel line was installed

a couple weeks ago from tank to pump. We checked all

the connections. What I thought could develope into a

major repair job turned out to be a $19 pump. We will see.

mike

 

[73vertproject]

Let us know, Mike. It did sound like the pump from your post.

 

[Valhallo]

Fingers crossed it's the pump. Based on my limited knowledge, it certainly sounds like it's the problem.

 

[goodnigh]

Let us know, Mike. It did sound like the pump from your post.

Even though I would like to drive my car, I do enjoy the hunt.

If that makes any sense.

mike

 

[rutkak]

Definitely could be the pump, fortunately they take 25 mins to change out and they are super cheap. They really don't go bad though, if ever.

The only other thing (if fuel is in fact the issue) could be a clogged sending unit in your tank. That's another cheap part but really that's about it (other than the filter of course).

Did you try spraying starter fluid in the carb while it was running to verify that it's a fuel delivery issue? If you spray fluid and it runs / idles fine then it's fuel delivery...if it runs the same then it might be your spark is jacked up.

KR

 

[caspianwendell]

Let us know, Mike. It did sound like the pump from your post.

+1

 

[wwhite72]

RobbMc is selling Cleveland pumps again. Hand built with good components and rebuildable. Cheaper model is for up to 550hp.

 

[72HCODE]

What was the condition of the fuel tank, was the fuel sender taken out and at least the filter sock cleaned. I don't remember if you had changed the tank or not. But if you have junk in the tank it would re clog the system.

One other thing... Remote possibility if the fuel vapor system is clogged which it can be it will cause feeding problems.

Start the engine get it running confirm its running poorly, then go open the gas cap and leave it off, see if the engine suddenly runs better.

If the vapor line is clogged with varnish it will cause vacuum in the tank and reduced flow to the carb and it would mask as a bad fuel pump.

For the fuel pump , check your oil, if it smells of heavy gasoline then you know the pump is leaking and no good.

It could be the fuel pump as well and that is a pretty easy change. But you want to make sure you don't have other issues.

If the vent is clogged and the tank was never changed I wouldn't screw around I would just replace the tank and sender and replace the vapor line to the charcoal canister at the engine bay.

Just to give an idea when I replaced my fuel system and took the original vapor line out it was 100% clogged with varnish goo, and the rubber hose connection above the tank had split from age allowing a vacuum. Not to form in the tank.

 

[rutkak]

+1 on 72HCode. That's sound advice.

 

[Wolverine]

1. Have you checked timing to assure advance is working properly?

2. Fuel Pump Test- Disconnect anywhere after fuel pump but before filter. Install long rubber hose on fuel pump side of disconnect, put other end into a milk carton. Crank car and see if you have fuel. If you have fuel, add fuel filter and see if you can pump gas past filter.

3. If you are really adventurous, count the cranks and see how long it takes to fill up the milk carton. That way if you do replace the fuel pump, you have a basis for volume delivery.

 

[Justin71]

Also do a basic check of vacuum on your system. We had a vacuum leak that would pull about 15in vacuum, you should have between 18-21in. My leak was at the carburetor to intake manifold interface. if anypart of this seal goes bad, you can lose enough vacuum to keep the car from running well. You can chck for this by spraying starter fluid all aroudn the base of the carb while idling. if the engine ever revs significantly when you spray somewhere, the starter fluid was sucked in thru the vac leak.

You of course can have vac lines go bad, and leak. just try removing the vac advance line from your dist. That should make a noticeable diff in how it runs. If not, you could have a vac leak. Check all the lines to make sure they are in good shape

Our car would run "ok" at idle, but not at reg driving speed, and the most noticeable thing was popping or back-firing at when coming off-throttle. I couldn't set timing no matter what I tried when I had this "little" leak.

It took me forever to get my little issue figured out - but it was highly educational for me to finally resolve it myself. you can read all the sordid details here:

http://www.7173mustangs.com/thread-after-firing-when-off-throttle

This forum was instrumental in getting me the knowledge I needed to get the problem worked out. There may be some things discussed there that help you. Hope so.

Jay

 

[goodnigh]

What was the condition of the fuel tank, was the fuel sender taken out and at least the filter sock cleaned. I don't remember if you had changed the tank or not. But if you have junk in the tank it would re clog the system.

One other thing... Remote possibility if the fuel vapor system is clogged which it can be it will cause feeding problems.

Start the engine get it running confirm its running poorly, then go open the gas cap and leave it off, see if the engine suddenly runs better.

If the vapor line is clogged with varnish it will cause vacuum in the tank and reduced flow to the carb and it would mask as a bad fuel pump.

For the fuel pump , check your oil, if it smells of heavy gasoline then you know the pump is leaking and no good.

It could be the fuel pump as well and that is a pretty easy change. But you want to make sure you don't have other issues.

If the vent is clogged and the tank was never changed I wouldn't screw around I would just replace the tank and sender and replace the vapor line to the charcoal canister at the engine bay.

Just to give an idea when I replaced my fuel system and took the original vapor line out it was 100% clogged with varnish goo, and the rubber hose connection above the tank had split from age allowing a vacuum. Not to form in the tank.

Very Good Advice!

All we know for sure is 1) Car runs crappy, 2) Sight windows in carb

are at half and when we start the car the bowls drain and do not

refill.

If we crank the engine without starting it the bowls refill only to be

drained again when the engine starts. Good suggestion on the vapor

cannister. I use a vented gas cap but don't know the condition of

the vapor line. Have not checked the oil for a gas odor but there is

an oil residue on the block where the pump mounts that should not

be there. Another quirky symptom, sometimes the starter has a hard

time cranking the engine. Both starter and battery are brand new.

Sometimes cranks right up and sometimes "lags" and has a hard time

turning the engine. One good thing about this event, it gave me an

excuse to buy a new toy

mike

 

[goodnigh]

We installed a fuel pump purchased from Summit Racing.

Turned out to be a bad fuel pump purchased from O'*****y.

Won't mention brands, but the one from Summit WORKS!

Car is happy!

mike

 

[72HCODE]

Great

 

[goodnigh]

Still ran poorly after the new pump.

The old pump was bad, we now have fuel.

We checked the vacuum lines and found

some deficiencies, fixed that. Adjusted the

idle screws and have 18mm Hg at the

manifold; good enough for a 770 Holley, stock

manifold and "mild" cam.

One thing I learned from this.

When we installed the new exhaust system purchased

from Don of OMS it changed the way the engine is tuned.

The old exhaust were glass packs (cherry bomb) with no

glass left. The new system is tuned for a Boss 351.

You will need to re-tune your engine. I did not think that

changing the exhaust system would have much effect on

how the engine is tuned. It does.

So those bends in the pipe mean something.

mike