Hi John.

I don't know how accurate my fuel pressure gauge is. Regardless, what
it shows pretty much coincides with the consistent symptoms.

I'm about 100% certain the fuel pump check valve is at fault but don't
see how it relates to engine temp. (or fuel pump temp?)

I'm running a Jetta engine with a Vanagon fuel pump. IIRC, PSI test
specs for the Jetta fuel system are nearly, or exactly the same, as
for the WBX.

My theory. Engine cold, the normal procedure of priming pump at ign.
on and running it while cranking engine, is enough to create and hold
fuel pressure to start engine. But.... Engine barely warm (upper rad
hose warm nearly cold to touch), bypass switch installed at 87 & 30 of
fuel pump relay socket, if I turn pump on for less than 5 seconds then
off, pressure drops to zero in less than 3 seconds. This may somewhat
simulate the fault when engine barely warm. I haven't tried starting
the engine while watching the fuel pressure gauge.

Prior to testing, repeated priming via ignition switch would not
suffice to start a barely warm engine. This now kind of makes sense
given the rate at which residual pressure drops in the above test.

Neil.

On 3/4/14, JRodgers <jrodgers113@gmail.com> wrote:
> Neil,
>
> I Have the same issue on one of my '88's. Hard start when warm. When
> cold starts immediately.
>
> I too would like to know what's with that!

--
Neil n

Blog: tubaneil.blogspot.ca

'88 Westy http://tinyurl.com/c8rlw6p

'81 VanaJetta 2.0 "Jaco"  http://tubaneil.googlepages.com/

Vanagon VAG *Gas* inline-VR Engine Swap Group:

http://tinyurl.com/d7gd5ej