SCarGo02

...for the Foxes.

I've been replacing vacuum lines -- I really need to replace the breather from the cam cover to the air box though, as it's in questionable shape.

I'll give the vacuum leak test a try and see what happens.

SCarGo02

1.) Drove the car for 15-20 minutes until it was warmed up. Came back home, turned the car off.

2.) After turning it off it immediately started back up with no problems.

3.) After 10-15 minutes it cranked a bit longer (maybe 10 seconds), stumbled, but if I held the pedal to the floor it started.

4.) After 20-30 minutes it wouldn't start no matter how much I cranked it (never for more than 20 seconds or so at a time). Pedal to the floor or not.

5.) After an hour (+/- 10 minutes) it started up pretty easily (pedal lightly depressed).

Drove it for another 20 minutes and there was no issues while driving. One thing I've noticed (which makes me believe there is a vacuum leak) is that when it's cold, it starts and the idle bumps up about 1500-1600 RPM when cold, then drops to about 1200 RPM once it warms up a bit. After driving it the idle goes up to about 1600-1700 RPM and stays there.

The fuel pump relay is warm (ot hot or anything I'd consider out of the ordinary) and the fuel pump is cool to the touch, even after driving. The control pressure regulator is pretty warm, but it is bolted to the side of the engine block...perhaps leading to a vapor lock condition. Although my 4-door has the same setup and never vapor locks (actually has the opposite problem - has problems starting cold but starts fine once it's even slightly warmed up).

I don't know if this helps the diagnosis or not, but I figured I'd post my findings.

shortyq

Found in the turbo CIS cars... A 3 second trigger relay that bypasses the cold start circuit. Powered on during cranking only, it pulses the cold start injector during warm cranking. On my urq, I actually added a bypass to it so that I could use a momentary contact switch during starting (A Steamboat Ice Track 6900ft problem). Easily added to all CIS cars, just use an override switch to ground on the cold start sensor.

Don't forget too, that the fuel pump Relays in the vw CIS cars were known problems. Removing the FPRelay from the fuse block helped the heat problem, but a second fuel pump relay all but eliminates this issue (common urq mod too)

HTH

Scott J

boxerfan

and then try and start the car. 10 seconds should allow enough pressure to build.

SCarGo02

...without starting car. Then try and start it after about 10 seconds of letting the fuel pump run?

SCarGo02

...simply triggered the cold start valve based on engine/coolant temperature?

I swapped in a brand new fuel pump relay that was in my 4-door Fox which didn't help.

My 4-door had the recall done when it moved it above the under-dash fuse block to it's own position. The GTI has it in the original '78 location though.

shortyq

The older cars used just the temp sender (ground) and starter circuit (positive) IIRC. The relay in the CIS turbo cars is a pulse type which can help prevent flooding. It can be added to any CIS cold start circuit. If the fuel pump is still in the fuse block, I'd do the fuel pump relay mod asap. Some of the hot start issues on the early vw were traced to that circuit.


HTH

Scott J

SCarGo02

Is there any documentation on the fuel pump relay mod?

boxerfan

It is actually part of a diagnostic proceedure I saw in the Bentley for 'I forget what'. But applying the idea to leaky injectors or a leaky fuel system in general if it takes 10 seconds to pressurize the system for correct readings then it must pressurize it enough for a discovery about injector leakdown... at least that's how my fuzzy logic works.

Tony Hoffman-4000Q

It sounds like the fuel pump check valve isn't holding pressure.

What happens is this, if there is no pressure in the system, you will be fighting the tendency of the fuel to boil out of the lines when you shut the car down hot. I've experienced exactly this before. Back in HS I drove a 76 Fox, and it acted just as you described till I finally replaced the check valve. However, the colder it was, the less time it took to start. BTW, you can bleed it out by jumpering the FP relay and pushing up on the metering plate till the injectors "sing". That's what I did, till I finally figured out what was wrong.

Tony