Noses over at WOT when at operating temperature

Turn the A/C off. p

 

Adam,
U might want to try pinching the return line close with a pair of vise grips and take it for a ride. U can do it right at the pump. My Bro inlaw had this problem for yrs. and couldn't find a solution. Turns out it was in the return system. We plugged the return line and problem went away. This has fixed many other Buicks with the same problem over the years. Hope one of these suggestions work for U.

 

Adam,

If I had a situation like this, I would go right a back and put the STG 1 pump back on it, and then see if the car returns to it's pre-fuel pump install state.

JW

 

JW - normally i'd agree with your suggestion,i.e. Eliminate the unknown variable ... But in this instance the stg1 pump was causing a very similar s)symptom

My suggestion would be to back-half the car

 

Ya, but the STG 1 pump lean out issue was different.. as I read his description.

I would want to isolate the fuel pump.. so by changing it back, and then running it around, if it goes back to how it was originally, you can quit looking at everything else.

Not a cure for the issue, just a diagnostic proceedure.

And old mechanic's addage "If it was busted, and you fixed it, and now it's busted worst.. go back to where you were fixin".

It still could be something besides the pump, but I would want to know that first.

As was stated, it could be sucking down a rubber line, and the new pump could have more suction, so it does it faster.. but we are gettin' out in the tall grass now.. :laugh: Especially since he has had the tank out, and I am sure the smart young man that Adam is, had sense enough to replace the rubber lines then.. right? p

If you want to try something now.. then get it all good and hot, and failing, and then remove the inlet line on the pump.. and install a vacuum gauge on that inlet fitting.

Start it up, and rev it a bit. It has to draw a minimum of 10" of vacuum, at 2000 rpm.

If it passes that test, then take the vaccum/pressure gauge, and temporarily T it into the pressure side of the pump, and see if it's running out of fuel, by taping that gauge to the windshield, and re-creating the failure.. minimum pressure on a Q-jet is about 3- 3.5 lbs at WOT.

But I would swap the pump back in first.. just to re-create the original condition, and then move onto the pressure/vaccum test on the new pump. Then your sure..

Wouldn't hurt to peek at the rubber lines while your there.

If that don't work, get the plasma cutter out and put a tube chassis under that thing. Don't laugh, I have seen guys do things like that.

JW

 

I just wet myself!

 

Hey Smarty, can you borrow a known good "performance pump" from someone for an hour or two?

 

I agree, I have seen bad wires cause it also...take a close look at your ignition system. If 2 pumps didn't cure the issue...

 

Cason said it in post number two.

What the heck is going on with fuel pressure at WOT?

Verify it's ok and move on.

Devon

 

Smarty.

The car is an obvious lemon, and I suggest you sell (I mean give) it to me.:laugh: :idea2:

 

For real! Everyone is giving all these complicated solutions, but checking fuel pressure covers pretty much everything.

 

I'm sorry Adam, I don't know of an easy way to do it other than to perhaps fab a test line to the carb that will give you the opportunity to fit a gage. If you can manage this it will help you rule out the fuel system regardless of what you do with the rest of the system.

I'm a fuel guy. finding a way to rule that system out opens up all the other possibilities.

Knowing this will help you with more tuning in the future.

Devon

 

This is how I did mine. My gauge is mounted permanently, and even though it's on a Holley I see no reason why you couldn't make up a tee similar to this for temporary use on the fuel inlet, something that could be installed inline without any cutting. I drilled and tapped this fitting for an 1/8" pipe thread and just a put a smaller 90* fitting in it for the gauge.

 

Exactly why i suggested back halfing it - new fuel cell, electric pump with high volume race can filter, 1/2" braided line to the carb ... Eliminates almost all points of trouble with one fell swoop

... Nobody ever takes me seriuosly o No: ou:

 

on an even more serious side, I can't see it costing you more than $15 or $20 bux to fab up a temporary MacGyver setup to replace the stock pump to carb feed line with some steel line, flare fittings, home depot stuff and some fuel injection rubber hose with a "T" for the pressure gauge. Not something I'd want to drive with for a season but for research purposes it'll do.

 

Just another little plumbing job. Testing rules. I had to do similar plumbing to add a filter inline B4 the carb- 67 carbs do not like those marine filters!