Car stalls - can't restart

[xray]

If there's any truth to the speculation that starting fluid is somehow easier to ignite...

"Most common flammable and combustible liquids have autoignition temperatures in the range of 300°C (572°F) to 550°C (1022°F). Some have very low autoignition temperatures. For example, ethyl ether has an autoignition temperature of 160°C (356°F) and its vapours have been ignited by hot steam pipes."

http://www.ccohs.ca/oshanswers/chemicals/flammable/flam.html

Gasoline's autoignition temp is around 500F

http://hypertextbook.com/facts/2003/ShaniChristopher.shtml

BTW, Mike that's a real cool tool you linked...I'll need to add that to my list!

[MikeW]

Gasoline's autoignition temp is around 500F

So is it possible that a weak spark would be less than that? I always figured that a spark was way higher.

[rdefabri]

xray - will do. I can't thank everyone enough...this is helpful, and at some point I think we'll pinpoint the issue!

[rdefabri]

OK - I've found the source of the problem, but not the cause.

To those who said it's fuel starvation - you were correct. For the life of me I couldn't figure out what was going on, so I went back to checking the carbs. I took the float bowl covers off and sure enough - they were as dry as the desert.

This couldn't be possible, I knew that the fuel pump was working - I checked it! However, I worked my way back and tried the fuel pump next. Bingo - the pump was not pumping any fuel. That explained the empty float bowls. I know I am not crazy, that pump was working just last week, so I took the pump off, disassembled it - nothing looked off. The diaphragm was fine, the valves were clear of sediment, no major issues from what I could see. I moved the lever to determine if the pump was functioning properly, and it was pushing/sucking air. To confirm, I put the fuel hose into a tank of gas and began pumping - it was shooting out gas like a geyser...so the pump functions FINE.

The next thing I checked were the hoses - both were brittle and there was a hole on the hose from the fuel filter to the pump, so I assumed that no vacuum was being created and that fuel couldn't be sucked from the filter into the lines to the carbs.

I replaced the hoses, re-assembled everything hoping it would work - no dice. I cranked and cranked, and got nothing. I checked the float bowls - again, dry. I removed the hose coming from the pump to the line feeding the carbs and cranked again - nothing.

So the issue lies at the fuel pump - it is not pumping fuel to the carbs. This is absolutely crazy because a) I know the pump worked when I checked it last week and I made it work by actuating the lever manually.

Some research indicates that low pressure between the pump the gas tank can cause the fuel to vaporize in the supply line if the engine temp or ambient temp is high. The day my car stalled, it was extremely hot, although the engine temp was normal. I highly doubt this is the issue, but I suppose it's possible. As I said, I know the pump works if I move the lever manually - is it possible that there is a problem in the head or with the cam?

I am happy I pinpointed the issue, but still perplexed as to what is causing the problem. Any suggestions?

[zbane]

Since it appears that the pump is indeed working (at least when off the car) perhaps there is simply a blockage in the fuel line between tank and pump? WAG, but worth checking, no?

On second thought, when you pull the pump off the car, are there any signs that it is getting fuel? If so, perhaps a blockage after the pump?

[rdefabri]

Well I thought that, but I pulled the line from the pump to the carbs, and no fuel pumped out. So that means the fuel isn't getting there from the pump.

So it's either some sort of vaporization (doubtful), a clog in the lines from the tank to the fuel pump (possible, but odd) or for some reason the pump isn't being actuated properly by the cam (possible).

I would have thought it was complete pump failure, but I did make it work, so I know fundamentally it's sound.

[MikeW]

To test both the pump and for a clog between the tank and the pump just run a fuel hose from the suction side of the pump straight into a fresh gas can and crank the engine over. If the pump is working it will fairly quickly empty the can (it will send fuel via the return line back to the tank). If all goes well the car will fire right up in which case I'd say you've got a clog. If the fuel gets pumped but the car doesn't start then you're back to a problem between the pump and the carbs. If fuel doesn't get pumped then you've either got a problem with the pump or a clog on the other side of the pump.

[rdefabri]

Mike,

True, but testing that won't definitively rule out either. However, there is/was some gas in the filter, and that wasn't pumping. Since the hose between the filter and the pump was brand new, I don't think there is a clog there, which leads me to believe it's the pump - it's not pumping well enough or it's not being actuated by the cam, not sure.

[JimmyZ]

If you have a compressor get a siphon sandblaster and use the pickup end to suck some fuel from the tank just upstream of the pump. Do it outdoors and away from any ignition sources! DON'T try this with a vaccum!! (=KABOOM! ) Allow any raw fuel to completely evaporate before continuing. Imagine dropping a wrench and having it spark. You might also try a handheld vaccum pump available at parts stores to check for fuel flow/blockage. (Much safer) The suction end of a hand sandblaster will spray a cloud of gas about 20 feet. Best to stop the moment any fuel begins to flow.

My bet is that the pump is bad or the cam bolt has loosened OR you need to add a couple more gallons of gas to the tank. It would take a lot to clog a 240's line. Now that I think of it it might be possible to have a clogged line if your tank liner went bad. (Assuming it was a refurbished tank) Isn't there an electric pump on later 240Z's??? If you have such a pump it might be the culprit. I'd definitely crawl under the car and have a look to see what it has. Perhaps someone put an extra filter in upsteam of the pump?

2c

Jim

[rdefabri]

My bet is that the pump is bad or the cam bolt has loosened OR you need to add a couple more gallons of gas to the tank. It would take a lot to clog a 240's line.

The pump is mechanical, not electric. Pumping by hand, it works absolutely fine. I took it apart, everything is fine - spring is taught, no rips/punctures on the diaphragm, the valves are clear and work. I did presume there was a problem with not enough gas, so I added 4 gallons to the 2 I had in there previously, no success.

I agree it would take a lot to clog the lines - the car died like it had no gas and when I checked everything yesterday, it was BONE DRY (no gas from pump to carbs/bowls!!!)

I have no way of knowing unless I remove the cam cover (which I think is the next step) if the cam bolt is loose. Something tells me there's intermittent (now permanent) failure since the car was working fine just 2 weeks ago. The fuel pump was squirting fuel, so I know somewhere in that area the failure lies.

[MikeW]

I have no way of knowing unless I remove the cam cover (which I think is the next step) if the cam bolt is loose. Something tells me there's intermittent (now permanent) failure since the car was working fine just 2 weeks ago. The fuel pump was squirting fuel, so I know somewhere in that area the failure lies.

All you have to do is remove the fuel pump and look in the hole to see if the bolt is loose. The fuel pump arm rides on a offset cylinder. You should be able to verify that the cylinder is rotating with the engine. If it is loose and therefore spinning freely you will have to remove the valve cover to fix it.

[rdefabri]

Mike,

Excellent - I will do that.

Out of curiosity - is this common? I would have thought the pump would fail prior to the eccentric!

Rich