1963 IIA 2.25 Dies when hot

[timc930]

After driving the IIA for approx 15-20min, car just feels like it run's out of gas, and it dies. Once it cools down it fires right back up and runs for another 10min or so and does it again. I am still gathering the facts on this, but the first thing I want to rule out is vapor lock, as to get it started this last time I poured some fuel into the carb and I could hear it bubbling, I guess from the heat of the exhaust manifold which is right under the intake. I am new the Series IIA's but not new to Carb's, as I used to work in old carburated 911's, so I am learning the idiosyncrasies of the IIA...

So when it died I did the following:
1) Disconnected fuel line at carb and manually pumped fuel to rule out blockage.
2) Cranked car and directed fuel into plastic container to verify FP working.
3) Checked for spark at each plug.
4) Unscrewed plug on bottom of carb fuel inlet and watch fuel come out while starting.
5) Pulled carb top off to validate fuel in the carb bowl.

Bottom line, I am getting spark and fuel (to a degree)...

Any thoughts on going to an elect pump like a facet and bypassing the mech pump, as I am really not sure that the mech pump is pumping the correct amount of volume of fuel as well....

Thoughts?

tim

[stomper]

Try opening the fuel cap when it stalls and see if you have a vacuum in the tank. There should be no pressure build-up, but if the fuel cap seals too tightly, this can cause fuel starvation issues.

[timc930]

Try opening the fuel cap when it stalls and see if you have a vacuum in the tank. There should be no pressure build-up, but if the fuel cap seals too tightly, this can cause fuel starvation issues.

Interesting, I'll check this out, thank you.

[jcadwell]

Are you sure you have spark? It could be the coil heating up and failing to deliver a hot spark. Had a porsche like that once...

[darbsclt]

It could be the coil heating up and failing to deliver a hot spark.

I second this...

My experience with Series vapor-lock symptoms has been...

If started cold - no issue... driving - no issues
If started while HOT - difficult/fuel starved... once started, it remains fuel starved and prone to stall when stopped until fresh/cool fuel circulates

My experience with a bad coil has been stalling/back-firing when hot and while driving. Usually at the most inopportune/embarrassing times - ex. crossing a busy intersection during rush hour (sigh).

The frustrating part is that a bad coil can mimic a fuel issue, compounding/overlapping symptoms. Also, be warned, new coils can fail straight out of the box.

Turning back to vapor-lock... these are some of the steps I took to minimize my symptoms...

- Installed a "summer" thermostat
- Added a thermal sleeve to my fuel lines
- Wrapped the base of my Carb in a thermal sleeve
- Added an inline fuel filter immediately prior to my carb (for some reason the PO only had one down at the tank)

All of this (combined) seemed to help quite a bit. Although I have an electric "pusher pump" installed, I haven't needed to use it since taking these steps.

Hope that helps...

[timc930]

I just replaced the coil, but that does not mean it's good. I have a few from old 911's laying around, are coil''s pretty generic?

Anyone know what the spec is for fuel pressure at the carb feed line?

[darbsclt]

Anyone know what the spec is for fuel pressure at the carb feed line?

The spec's I've seen are ~ 3psi for the mechanical pump.

Note: I don't know how much trust you can put in the readings of 'off the shelf' fuel pressure gauges. I used a Holley gauge on mine & it read 9psi. Rather than the actual reading, I paid more attention to consistency in readings in order to judge the health of my mech pump.

BTW: Have you mentioned what carb you're running?

[timc930]

BTW: Have you mentioned what carb you're running?

Single barrel, have to look to see if it's Zenith/Solex. I have a 2brl Weber and manifold (new) that came with the truck, just not sure of the benefit on the 2.25.

Oh yeah, gas mileage is around 10mpg! So I definitely have some issues.

I picked this truck up last year, but due to being out of my house and garage due to home renovation I have not been able to do anything with it. Should be moving back into the house late this month and then I'll be able to spend some time with the little truck!

Just tinkering now, and planning for the work I am going to do this fall and winter...

[stomper]

Coils are pretty much universal, as long as it is a 3ohm primary resistance. (all 4 cyl engines run 3ohms)

[yorker]

There is a fuel filter you can get that returns excess fuel to the tank, thus keeping the fuel supply rather cold. Some here have used it to cure vapor lock. Similar to this one:
http://www.ebay.com/itm/3040-NAPA-GOLD-FUEL-FILTER-/380996335264?pt=Motors_Car_Truck_Parts_Accessories&fits=Make%3AJeep&hash=item58b526b6a0&vxp=mtr

[timc930]

So I have ruled out the coil, fuel pump, and vapor lock. Drove it today with the gas cap off, and once hot, it died. When car dies, I have excellent pressure at the Carb, as I pulled the line off at the carb and fuel sprayed everywhere. There is plenty of fuel in the carb bowl as well. I can also use the hand pump on the bottom of the FP to pump fuel when it's hot, so the FP diaphragm appears to be good. So I think my fuel delivery to the carb is fine. I am wondering if I have a problem getting the fuel from carb into the combustion chamber.

What I am curious about, is just before it stalls it runs as if it is not getting fuel, or loosing fuel pressure, as I can drive at a constant speed, but if I try to accelerate it feels as if it is running out of gas, then just dies. Bottom line, the engine will not take any additional load, and is somewhat difficult to maintain existing load, then it just dies. So when I pour fuel down the carb to get it to restart, there is a tremendous amount of bubbling, so, can the manifold be getting to hot causing the fuel to evaporate before it goes into the combustion chamber?? Logically this could be the cause, just don't know if it is realistic....

[yorker]

Did you figure out which carb you have?

[timc930]

Did you figure out which carb you have?

Weber 34ICH.....I have a Weber progressive 2BBL and manifold that came with the truck that I may stick on it later if needed....

tim

[yorker]

Definitely not the Weber 1 bbl then? Jets are clean?

[timc930]

Definitely not the Weber 1 bbl then? Jets are clean?

Just went and picked it up, fired right up and drove back to the house...

I stand corrected, I have the Weber 34 ICH.

And yes jet's are clean, needle and seat works. I pulled the carb apart several months ago and did a cleaning/rebuild....

tim

[yorker]

With a Weber that really doesn't mean much they'll clog with the slightest bit of stuff and it is surprising how much passes the filters. How much choke does it need when running cold? Also do you have the phenolic block on the intake in between the manifold and carb?

[timc930]

With a Weber that really doesn't mean much they'll clog with the slightest bit of stuff and it is surprising how much passes the filters. How much choke does it need when running cold? Also do you have the phenolic block on the intake in between the manifold and carb?

I pulled the top off a couple of weeks ago to check the needle and seat, and to ensure the bowl was filling. Spotless inside. I've spent hours and hours with carb's (Zenith) on old 911's dealing with trash inside, and this just does not feel the same, as it runs fine, takes full throttle until it get's hot.

Yeah, I have the phenolic block, well it was on the truck when I got it.

Strange thing, is that this just started happening, without any changes as I drove the truck for a year with very little issues, although it has always had what I thought was a fuel flow to cylinders issue.

Should the fuel act like it is "boiling" when poured into the carb? If so, then I have another problem....

[yorker]

Fuel will boil on the manifold, or in the intake manifold when the engine is hot because the exhaust manifold heats it(as designed). Ethanol blends may lower the boiling point too.

[timc930]

Fuel will boil on the manifold, or in the intake manifold when the engine is hot because the exhaust manifold heats it(as designed). Ethanol blends may lower the boiling point too.

Then I may have another problem. This is really odd, as it definitely feels like it is running out of gas when hot, but nothing has changed, so has to be some part failing, as the operating environment has not changed. I'll go back and recheck spark and fuel.

So the other odd thing is, if I let it just sit and idle until it gets hot, it will idle fine, but it will not take throttle as crisp as when warm, and it will NOT take a load at all, that will cause it to die and not restart. So as it gets hot, the volume of fuel getting into the cylinder is reduced for whatever reason...

[yorker]

http://www.aloharovers.com/tech/ichoverhaul.htm

http://www.glencoyne.co.uk/carbs.htm

Well let us know what else you find.

[jcadwell]

How about heat soaking the distributor? Are you running pertronix or points?

[LaneRover]

Have you moved the fuel line? or Changed the fuel line to a different material?

[timc930]

SO this is definitely a fuel problem, as I drove it today a short distance and just as it was getting hot I reached my destination. Let is sit for about 30min while I took the dogs for a quick walk. The truck would not restart without first pouring a bit of fuel into the carb.

I have not changed the lines, but I have slightly moved the top of the fuel line where it peaks (height) at the top of the engine, the make a turn to go to the carb....

[yorker]

Any progress?