HELP - Carb Compression test + won't run...

Hi guys, need a bit of help with my dead 1781 Clipper Cabrio.

Question 1: How do you stop fuel to a carbed engine, to do a compression test on it? Is there a low pressure pump to remove the fuse from?

Question 2: Is it a head gasket failure?

- It ran when I got it, but spluttered on occasion and definitely wasn't 100%. It hasn't been on a long journey in a long time.
- It has always run badly, requiring a bit of throttle as well as the choke to get it running and keep it there.
- The exhaust is very smokey, and definitely has an oily blue tinge to it.

Yesterday I got it to run to get it out of the garage and into the sunshine for a bit (damp!). When i returned to it later it turned and spluttered on occasion, but didn't run. If it did fire it died instantly.
I have changed:
- Plugs
- Fuel filter
- Air filter
- Oil and filter
And I have also checked dizzy and rotor arm, and the HT leads look OK.

It's very fuelly in the cylinders - stinks.

I really don't want it to be HG. cf_emoticons__BangHead:

Clamp the fuel line would be the easiest option.

fuel pump is mechanical so take the fuel feed off the fuel pump or the feed to the filter, there will still be a fair bit of fuel in the carb though.

best bet is whip out the spark plugs and just leave it for a few hours to dry out, buff up the plug tips if they look grotty

Just to follow this up, we did a compression test by clamping the intake fuel hose temporarily.

Unfortunately the results showed that cylinders 2 and 3 were both extremely low on compression, and the other two were lower than expected too. So I think it's replacement engine time.

Thanks for the advice guys.

Have you checked if it's bottom or top end at fault?

Not yet. It's a 170,000 mile engine so when it read low on compression i just sort of packed up, went home and started looking on eBay…

Turns out the 1.8 carb engines aren't ten a penny like I thought they were…

I'm running a 1.8 out of a MK3 golf. Most of the ancillaries bolt up you just have to get creative with the fuel pump.

Surely for that you need an injection fuel tank too, not to mention the masses of wiring?

It's already got a manual choke on the car, and a very clean looking carb, so i'm guessing it's had a weber conversion at some point. I think I need to either replace like-for-like, or repair what i've got…

Only if you keep the injection system. I've got a carb inlet manifold bolted to the head.

I never thought that they would have been the same engines. I had a 1781 SPI Golf a few months ago that I sold for next to nothing…

So the mk3 engine all bolts up, including carb inlet mani, exhaust, clutch and box, ancilliaries, and it's just the fuel lines you have to get clever with?

did you test it with the throttle wide open? if not it'll throw out the results

Not the best pic but here's a 1999 mk3 golf engine running a carb in my clipper.

rubjonny said

did you test it with the throttle wide open? if not it'll throw out the results

No, but there was over 100PSI between the two outside cylinders and the two inside ones - not a difference that WOT could make to the readings

Very nice, Jay. Thanks for the pic. Have you used the Mk3 gearbox as well? It looks very shiny!

Yeah that does point to rings, valves or possibly HG.

Previous owner fitted the engine and I'm pretty sure it's the original box although he said it had a new clutch.

The only issue I've had was adjusting the timing as Mk3 flywheels don't have a timing mark, only a TDC mark. I've just set it by ear as I don't have a timing gun with a degrees setting.

try it again with the throttle wide open, you would be surprised how much it affects it

So my mechanic friend came to give me a hand with this at the weekend. To follow this up:

It wasn't HG!!

For those in the future that may have the same issue:

He described to me on the phone "bore wash" (petrol washing away the protective oil film on the bores) - something that was new to me.

He asked me whether the compression test we did was wet or dry. We did it dry, and the compression was very low. First thing we did on his arrival was pop a tiny bit of oil in the cylinders, turn it over a few times, then conduct another test.

We had compression!

After some hunting around we also found some perished vacuum lines and fuel hoses. With them patched up enough, we tested again and the car fired up no problem!

Now all it needs is a good drive. Thoroughly pleased with that outcome!

The symptoms were:

andrew_baran said

- It ran when I got it, but spluttered on occasion and definitely wasn't 100%. It hasn't been on a long journey in a long time.
- It has always run badly, requiring a bit of throttle as well as the choke to get it running and keep it there.
- The exhaust is very smokey, and definitely has an oily blue tinge to it.

Yesterday I got it to run to get it out of the garage and into the sunshine for a bit (damp!). When i returned to it later it turned and spluttered on occasion, but didn't run. If it did fire it died instantly.
I have changed:
- Plugs
- Fuel filter
- Air filter
- Oil and filter
And I have also checked dizzy and rotor arm, and the HT leads look OK.

It's very fuelly in the cylinders - stinks.

Cheers.