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Vapor Lock, Bad Fuel Pump, or ??? (fuel starvation issue)
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schmiddj
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PostPosted: Tue Feb 25, 2014 12:11 pm    Post subject: Vapor Lock, Bad Fuel Pump, or ??? (fuel starvation issue) Reply with quote

Greetings Everyone,

I've perused the forums extensively and read up on vapor lock issues, but nothing has produced a solution for me - I'm looking for some direction on how to troubleshoot this further. Here's a brief background on my issue:

'67 1500 M157, Solex 30/31 PICT, Bosch 009 w/ electronic ignition, alternator. Complete rebuild in '12, about 7K miles driven since. Since around 4K miles after rebuild I've been experiencing what appears to be vapor lock. It started very gradually, with slight hesitation in the engine after driving at highway speeds for a few minutes and nothing more. Over time it became more severe, causing complete fuel starvation of the engine. Nowadays it occurs after the engine reaches operating temperature, with the engine stalling virtually every time I drive for a few minutes above 30 mph, and refusing to start until cooling for several minutes. I have an electric backup fuel pump mounted under the fuel tank which, when turned on, allows the engine to run normally. Although I can leave the electric pump on and drive without issue, I'd rather get to the bottom of this and use the electric pump as a backup only.

Here's what I'm seeing under the engine lid after the engine quits: there is a fuel filter between the engine-driven pump and the carb that is almost completely devoid of fuel, and the incoming fuel flow from the pump is almost cut in half by bubbles. Using a laser-thermometer, the filter and the pump are around ~110 deg F, the base of the pump where it mounts to the block is ~175 deg F, the heat riser is ~250 deg F, and all fuel lines are below 140 deg F. The oil dipstick is cool enough to rest my hand on it, although it is very warm. The valve covers are ~210 deg F. After the engine sits for a few minutes, the engine-driven pump heats to ~135 deg F, and gas can be seen bubbling up the fuel line into the filter before the carb. After several minutes of cooling, the engine will idle just fine - the problem returns after reaching roadway speeds.

I've checked the fuel tank for a venting issue - no "whoosh" sound when opening the cap. I've checked the fuel pump flange for binding of the push rod - it drops without hesitation into the block and doesn't seem to be too tight (granted, I haven't checked this when the engine is hot). I've wrapped the german fuel lines with insulating aluminum tape to protect them from heat in the engine bay - no improvement. I've installed deck lid stand offs - no improvement. No fuel smell coming from the oil and no fuel leaking out of the pump when I remove it.

A couple of notes: The outside temperature has been around 50-70 deg F, and I'm getting around 20-23 MPG. I haven't checked the carb jets - I would guess the 30/31 carb is jetted too lean because I get occasional backfiring when suddenly letting off the throttle. The engine-driven fuel pump appears to be an aftermarket design (see attached pictures); it has the alternator-style angle and it appears to have the proper push rod (4" length). I don't have a cylinder head temp gauge, so I can't check that.

Anyone have any ideas? Would a pump rebuild/replacement be prudent? Could the engine still be running too hot even considering the temperatures I've observed? For those still reading at this point - thanks for reading my great American Beetle novel!

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carcrazed
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PostPosted: Tue Feb 25, 2014 1:45 pm    Post subject: Reply with quote

I would try moving your fuel filter underneath the car ESPECIALLY those plastic ones.
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djshutup
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PostPosted: Tue Feb 25, 2014 2:04 pm    Post subject: Reply with quote

what is the PSI of the current fuel pump you have?
When the car dies and refuses to start pop the top of the carb and see if there is any gas in the float bowl.
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schmiddj
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PostPosted: Tue Feb 25, 2014 11:31 pm    Post subject: Reply with quote

vwkind wrote:
what is the PSI of the current fuel pump you have?
When the car dies and refuses to start pop the top of the carb and see if there is any gas in the float bowl.


Not sure who made the fuel pump and I don't have a gauge so I couldn't say what psi it should be (or is) putting out - although the electric pump shouldn't put out more than 4 psi. The carb bowl is bone dry after the engine dies. Turning on the electric pump provides enough pressure to refill the bowl before restarting, although that clear filter bubbles for a good few seconds before filling again (also giving off a faint smell of gas Shocked , although no leaks observed). As soon as I receive some new 5mm hose and filters, that engine bay filter is gone...
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djshutup
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PostPosted: Tue Feb 25, 2014 11:42 pm    Post subject: Reply with quote

schmiddj wrote:
vwkind wrote:
what is the PSI of the current fuel pump you have?
When the car dies and refuses to start pop the top of the carb and see if there is any gas in the float bowl.


Not sure who made the fuel pump and I don't have a gauge so I couldn't say what psi it should be (or is) putting out - although the electric pump shouldn't put out more than 4 psi. The carb bowl is bone dry after the engine dies. Turning on the electric pump provides enough pressure to refill the bowl before restarting, although that clear filter bubbles for a good few seconds before filling again (also giving off a faint smell of gas Shocked , although no leaks observed). As soon as I receive some new 5mm hose and filters, that engine bay filter is gone...


If you got a harbor freight near you
http://www.harborfreight.com/fuel-pump-and-vacuum-tester-93547.html
don't forget the 20 or 25% off coupons floating around the net.

That style pump you have I've tried one like it and the PSI was like 3x too high. I didn't have the problems you did but I had problems. I keep a plastic filter in the engine bay and on first start of the day I get air bubbles. Also mine is almost bone dry after sitting a while and when running only ~1/3 full. When you run the electric pump your running both fuel pumps @ same time or do you bypass the engine pump?
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Kiptere
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PostPosted: Wed Feb 26, 2014 6:02 am    Post subject: Reply with quote

A lean running engine runs hot. I rejetted my H30/31 to a 125 main jet - got rid of the 1st gear hesitation as a bonus. Have you thought about running dual oil coolers? Mount the second one behind the big hole on the back of the fan shoud. Why don't you just stick with the electric fuel pump and don't worry about it?
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PostPosted: Wed Feb 26, 2014 7:36 am    Post subject: Reply with quote

My 67 bug was doing this same thing but in much hotter, Phoenix temperatures. I found that I had routed my steel fuel line incorrectly in the engine compartment. It was picking up heat from pre-heat tube on the carb manifold. I rerouted it and covered it w/larger fuel hose to be sure. I also replaced the fuel pump as I suspected it wasn't pumping the fuel as well. These two things corrected the problem.

The other thing you answered was checking to see if the carb bowl was empty after you stopped the car. If the bug is running normally when you shut it down then the bowl should have gas in it. So, when you go back to the car and it won't restart, it makes me wonder where the fuel went? Is the carb leaking fuel? The fuel should should still be in the bowl. Does it restart for a few seconds until the fuel in the bowl is burned then it hits fuel starvation?
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schmiddj
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PostPosted: Wed Feb 26, 2014 10:53 am    Post subject: Reply with quote

Kiptere wrote:
A lean running engine runs hot. I rejetted my H30/31 to a 125 main jet - got rid of the 1st gear hesitation as a bonus. Have you thought about running dual oil coolers? Mount the second one behind the big hole on the back of the fan shoud. Why don't you just stick with the electric fuel pump and don't worry about it?


Next on my list of things to do is re-jet the carb - I need to check what jets are in it now but I'm guessing an X112 main (super lean). If anyone has other jetting recommendations for an H30/31 (roughly sea level, hot/dry climate) I'd love to hear them.

wcfvw69 wrote:
The other thing you answered was checking to see if the carb bowl was empty after you stopped the car. If the bug is running normally when you shut it down then the bowl should have gas in it. So, when you go back to the car and it won't restart, it makes me wonder where the fuel went? Is the carb leaking fuel? The fuel should should still be in the bowl. Does it restart for a few seconds until the fuel in the bowl is burned then it hits fuel starvation?


If it's running NORMALLY when I shut it down, the bowl is filled (the only way it runs normally is with the electric pump on, pumping through the mechanical pump). With the electric pump off, the engine dies as described above - in THIS case the bowl is empty. The engine won't restart until the bowl is refilled with the electric pump or I allow the engine to cool for several minutes, after which I presume cranking it refills the bowl with the engine-driven pump. I can't see any fuel leaks in or around the carb, so I don't think that's the issue.

I could simply bypass the engine-driven pump and use the electric pump, but I'd rather reserve the electric pump as a backup (also, it's fairly noisy and can be heard in the cabin). Thanks for all the responses so far!
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PostPosted: Wed Feb 26, 2014 12:47 pm    Post subject: Reply with quote

If you not cooking the fuel line in the engine compartment and theirs no restriction on the fuel coming to the pump (clogged fuel line or filter), it would be a quick check to buy another $20 dollar fuel pump to rule that out.

I had a fuel pump start to fail. Luckily for me, it didn't leave me on the side of the road. I was entering the freeway and it was starving for fuel and I couldn't get up to speed. The pump simply couldn't keep up with the volume to keep the carb full. I swapped fuel pumps and the problem was solved.
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DrKeck
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PostPosted: Wed Feb 26, 2014 1:08 pm    Post subject: Reply with quote

check the Psi coming out of your fuel pump. X2 on the harbor freight gauge
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PostPosted: Wed Feb 26, 2014 1:14 pm    Post subject: Reply with quote

How is this "backup" fuel pump plumbed in your car? Actually what is the full routing for all your fuel lines, where do they all start and end? It makes no sense to me why you'd even have one in the first place.
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PostPosted: Wed Feb 26, 2014 1:31 pm    Post subject: Reply with quote

If you electric pump is inline to the mechanical fuel pump it will restrict the fuel flow and could be causing your problem.
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PostPosted: Sun Mar 02, 2014 5:50 pm    Post subject: Reply with quote

jhoefer wrote:
How is this "backup" fuel pump plumbed in your car? Actually what is the full routing for all your fuel lines, where do they all start and end? It makes no sense to me why you'd even have one in the first place.


Turns out the electric pump is routed inline with the fuel line to the engine-driven pump... so that's not helping. The full routing is as follows: fuel tank > rubber hose to plastic fliter > rubber hose to electric pump > rubber hose to steel line (through tunnel) > rubber hose to engine-driven pump > rubber hose to plastic filter > rubber hose to carb. The electric pump was an addition by the previous owner, and I can't say why he added it. The peculiar part is that the engine ran fine for a year after it was rebuilt - the vapor lock/fuel starvation issue began over 3,000 miles after the rebuild. The filters do look pretty dirty, though...

What's the best way to route the lines so that the engine-driven pump isn't forced to draw through the electric pump? Or am I just avoiding the obvious solution of using the electric pump only (I hate how loud it is)?

Thanks again for all the help!
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PostPosted: Sun Mar 02, 2014 6:21 pm    Post subject: Reply with quote

Try running a line without the filter under the tank. I know in my situation my beetle refuses to run right if I put a fuel pump anywhere before the fuel pump. You said your filter is dirty have you check the sock in the gas tank? If that screen is all boogered up that would cause some serious fuel problems.
It sounds like your running 2 filters at the same time...is your tank that bad?
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PostPosted: Sun Mar 02, 2014 7:36 pm    Post subject: Reply with quote

That could be your problem right there. The electric pumps if not pumping can act like a stopped up fuel line. So at high speeds it keeps fuel from lowing fast enough to fill carb. Dirty fuel filters don't help either.
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PostPosted: Mon Mar 03, 2014 11:02 am    Post subject: Reply with quote

schmiddj wrote:
What's the best way to route the lines so that the engine-driven pump isn't forced to draw through the electric pump? Or am I just avoiding the obvious solution of using the electric pump only (I hate how loud it is)?


You would have to run two separate lines all the way from the tank and Y them together at the carb. Assuming that both fuel pumps' check valves are working to prevent reverse fuel flow.

Tank fitting 1 -> Filter 1 -> electric pump -> Y fitting -> carb
Tank fitting 2 -> Filter 2 -> mechanical pump -> Y fitting -> carb

The benefits of having a redundant fuel pump seem marginal at best. Personally, I'd just keep it simple and only use one pump. If you eliminate the electric pump you might find your mechanical pump works just fine.

Go buy a splice fitting for your fuel line and bypass the electric pump. Cap the ends on the fuel pump to keep dirt out of it. Then if the mechanical pump ever fails and you have need of the electric pump, you remove the splice, reattach the fuel lines, take the splice fitting and bypass the mechanical pump lines.
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PostPosted: Fri Jun 27, 2014 6:27 pm    Post subject: Reply with quote

Did you ever get this issue fixed?

I'm having a similar issue. Newly installed engine. Had 30 Pict-1. Idled good. Ran through third gear with normal driving. In fourth I had fuel starvation symptoms and she stalled. I could restart almost immediately with little to no cooling. Does seem to be running a little hot but nothing crazy. I had a properly tuned 28 Pict so I swapped it on thinking the 30 may be lean (which shouldn't be the case). Same symptoms with the 28 Pict.

I'm thinking fuel pump, but I suppose it could be vapor lock. Thoughts?
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PostPosted: Fri Jun 27, 2014 6:27 pm    Post subject: Reply with quote

Did you ever get this issue fixed?

I'm having a similar issue. Newly installed engine. Had 30 Pict-1. Idled good. Ran through third gear with normal driving. In fourth I had fuel starvation symptoms and she stalled. I could restart almost immediately with little to no cooling. Does seem to be running a little hot but nothing crazy. I had a properly tuned 28 Pict so I swapped it on thinking the 30 may be lean (which shouldn't be the case). Same symptoms with the 28 Pict.

I'm thinking fuel pump, but I suppose it could be vapor lock. Thoughts?
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PostPosted: Fri Jun 27, 2014 9:42 pm    Post subject: Reply with quote

jpeters wrote:
Did you ever get this issue fixed?

I'm having a similar issue. Newly installed engine. Had 30 Pict-1. Idled good. Ran through third gear with normal driving. In fourth I had fuel starvation symptoms and she stalled. I could restart almost immediately with little to no cooling. Does seem to be running a little hot but nothing crazy. I had a properly tuned 28 Pict so I swapped it on thinking the 30 may be lean (which shouldn't be the case). Same symptoms with the 28 Pict.

I'm thinking fuel pump, but I suppose it could be vapor lock. Thoughts?


Post some pics of your engine and provide some info on it. What size, etc..
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**Restored German Bosch distributors for sale or I can restore yours**
**Restored German Pierburg fuel pumps for sale or I can restore yours**
**Restored Porsche fuel pumps or I can restore yours**
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PostPosted: Sat Jun 28, 2014 4:22 am    Post subject: Reply with quote

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New 40hp. Pics shows the new 30 Pict before I swapped it out. All engine tin is there except for sled tins. If it is vapor lock it is occurring within about a minute or two of regular driving. I don't think it could be heat related in that time frame. I did find a piece of the fuel line near the heat riser that I'll fix, but I'm still thinking a fuel flow problem.
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