63 Spyder..need help...

[Grandpacorvair]

Hi giys,

I had the return of a problem I thought I solved last year...

First it's 1963 Spyder with an electric fuel pump mounted behind the tank. It does not have the mechanical pump.

Our club went on it's annual Fall color tour that consisted of about 200 miles highway and back roads. On the way home, at about 70mph, the car started bucking, then the speed dropped off. I let up on the gas, let the car coast down to 60mph, gave it gas and it ran fine. Ran it back up to 70mph and it began to buck again, then basically stopped running until the speed dropped to around 60 and then started back up. It did this several times then began to run fine at speed. Drove several miles at around 70-75 and then it started all over again. Not fun on an expressway!

I acts like it is running out gas. If I stayed below 65 it was fine.

I did notice a possible indication in that it seemed to be worse when going uphill, when going downhill I could get it over 70. I can't be sure this is completely accurate as there weren't lot of hills. Kicking in the turbo made the problem worse.

The fuel pump is new (clarks) and was replaced because of this issue late last year. The fuel filter is new and the carb was rebuilt two or three years ago.

The temperature was under 60 degrees. I was thinking vapor lock but not sure it would behave this way...

Not sure how to approach this problem...

Any suggestions appreciated...


Kerry

[bbodie52]

I'm trying to look at the possibility of other causes other than the initial assumption of possible fuel starvation. When you are pushing 70 mph, are you also starting to engage the boost from the turbo at that point? Is there enough horsepower demand at 70 mph, when climbing hills, etc. that boost from the turbo is coming into play, possibly creating a detonation condition? I was thinking that the possibility of an undetected issue with the pressure retard device or too much advance, or perhaps a batch of substandard Premium fuel with too low an octane was promoting a detonation condition that would cause the engine to "buck" or to run poorly if detonation was, in fact, occurring. At 70 mph pinging, or the rattling sound of detonation in the cylinders might not be audible, but it might be felt in the form of a poorly running engine. Under the circumstance you described you backed off of the throttle and slowed down, possibly taking the engine off of boost and promoting normal operation. But when you started climbing a hill or pushed the speed back up it is possible that the engine turbo was coming back online and placing the engine back into the detonation-causing range again.

It is only a theory, but it might explain what feels like fuel starvation—but might be something else entirely. Years ago I pushed my turbo engine too hard one time on an uphill grade highway at 70+ mph under similar conditions but did not back off of the throttle, until a hole appeared in a piston!

You might try a test drive while monitoring the boost gauge, to see if the poor engine operation coincides with positive boost from your turbo.

[Grandpacorvair]

Ugh, I hope it's not that....

There was no indication the engine was entering boost. I was simply cruising along and the boost gauge was significantly below 0. Didn't hear any pinging though my car isn't too quiet at 70mph! I might not have heard it. After it starts to buck and then bog down it feels just like if I were to turn the key off, then back on when the speed drops down below 60 or so. One time, when it was dropping off, I tried pumping the gas pedal several times and there was no response.

[terribleted]

Check the pump pressure and flow. Are you sure the fuel filter is not dirty restricting the flow of fuel? Sounds like fuel starvation to me. This is exactly what happens when a fuel filter plugs up.

[Grandpacorvair]

Good morning,

Of course, in the light of a new day I am starting to question my original 'diagnosis'. The car is also equipped with a Pertronix I module. Can anyone think of a scenario where the Pertronix might be the issue? It is an older version, likely close to 12 to 15 years old.

A fuel issue is still high on my list though... I can't think of any way to monitor the fuel pump pressure while driving at 70 plus mph!. The fuel filter was new last year so I don't think it's the problem, however anything is possible. One thing that I have come up with is a partially clogged/plugged sock in the gas tank. I'm not exactly sure how to verify that though...sounds like a project and a half getting it out..

Along the lines of monitoring the fuel pressure can someone recommend a good gauge I can install?

Thanks,

Kerry

[bbodie52]

I have heard of the early ignition module design failing if the key is left on for an extended period without the engine running, but I believe this can cause a complete malfunction. According to the Clark's Corvair Parts catalog, page 75A, the IGNITOR II design protects itself from this type of damage. I suppose a fault at a higher rev range is also a possibility. A failing aging coil could also be a possibility.

With regard to the fuel pump, I don't know the specifications for the electric fuel pump, but they may be available with the original documentation or on the manufacturer's website. Both fuel pump pressure and volume must be considered. The Corvair shop manual specifications state an expected fuel volume of 1 pint in 40 seconds or less (from the mechanical pump at cranking speed), and a pump pressure of 4-5 pounds (at 500-1000 rpm). The electric pump should produce a similar volume or better. If the pump produces normal pressure but a low volume, a leak on the suction side, or a partially blocked feed line or clogged fuel inlet filter might be the cause, and this could potentially cause a fuel starvation problem when the engine is running at a high consumption rate.

[Grandpacorvair]

Thanks for the information. The figure for volume should help, at least as a base line.

I tried suggesting to the better half that after I install a fuel pressure gauge, maybe she could ride in the engine compartment while we run the freeway at 70+mph to read the gauge...

Needless to say she was less than enthused..... [grin]

Kerry

[bbodie52]

...I tried suggesting to the better half that after I install a fuel pressure gauge, maybe she could ride in the engine compartment while we run the freeway at 70+mph to read the gauge...

Needless to say she was less than enthused..... [grin]

I dunno why? There is plenty of room on top of the flat engine, she could hook her feet under the intake manifold tubing (to keep her from flipping over backward under hard acceleration), and if you leave the engine compartment open the sheet metal in front will serve as a windshield. The louvers will even provide a bit of fresh air!

Kinda like ridin' a motorcycle. Drill a ½" hole (or larger) in the side of the float bowl and install a sight glass, to monitor the fuel level.

[miniman82]

Could be an overheating coil too, but sounds more like the float bowl getting sucked dry. My car would cook the coil in short order on the freeway, solution is to get an aftermarket coil (pick your poison) and move it to a cooler location- like not on the engine.

[terribleted]

Brad mentioned something above. The first thing I would do is look is at all rubber hose connections in the system...particularly any before the pump. These connections must be leak free or fuel delivery may be effected. When in doubt replace the hose and clamps. You should find these joint at the tank exit, likely before and after your electric pump (if the pump has a filter on it check it while your there), and above the left rear wheel where engine line mates to body line.


Fuel pump pressure is not speed dependent. Electric pump runs as it runs when it is on regardless of speed. You need only a simple pressure gauge capable of reading about 7-10psi....you might find a combo vacuum/pressure gauge at the local parts store that will suffice. As far as fuel volume the pump should deliver at least a pint in 40 seconds or less. Pretty easy to do these checks with an electric pump...disconnect one line from a carb and run the pump with the line hooked to a gauge for pressure or into bucket for volume measurement.

[Grandpacorvair]

So.... I finally did get around to checking flow volume and it's not what was posted above. In two tests it took slightly over a minute to get to one pint. I guess I'll have to check the pump pressure too. Looks like I am going to have to explore the fuel lines from the tank back to the carb. (NEXT SPRING) The list of things to fix grows ever longer...

[miniman82]

If that's true, you likely have a plugged sock in the tank or the pump is bad. Take the pipe off the bottom of the tank, and observe how quickly the fuel flows out. If it's slow, your sock is probably gummed up. If not, the pump might be plugged/bad.

[terribleted]

If that's true, you likely have a plugged sock in the tank or the pump is bad. Take the pipe off the bottom of the tank, and observe how quickly the fuel flows out. If it's slow, your sock is probably gummed up. If not, the pump might be plugged/bad.

Exactly.