My Z faded out...

[TimFZ]

Hi all, been out and about in my Fairlady z today but had an issue coming home when coming off a dual carriageway, it started to miss and splutter a bit. Then on the next hill very little power and then died.

Re started it then drove another half mile with little power, next hill died (so doesn't like higher revs or half throttle plus).

Then half mile on, did 100 yards or so then same issue but getting worse.

I'm thinking possible fuel issue but just wondered if anyone else experienced this or has some things I could try or test.

For info, it's a L20 with twin hitachi flat top carbs. Not yet colortune but will soon.

Cheers!

 

[Rob Gaskin]

Common fault if it's a blocked fuel filter. I've had that twice. Small particles of rust (like dust) come from the tank.

 

[TimFZ]

Great, OK will check that, it has a modern small filter by the tank. Is the problem low pressure for the pump (I have an electric pump, not using the mech pump and yes I can hear it spinning) due to blockage or that the crud gets to the carbs? I did fill up a bit today so could have disturbed it.

 

[Rob Gaskin]

It doesn't matter what pump you have. I've had a facet pump (internal filter) block and the OEM filter in the engine bay on another car.

 

[dav118118]

Try disconnecting fuel line near the carbs and then turn ignition on to check fuel flow. Make sure you have a container to catch the fuel.

it could also be some crud getting trapped in the float valve of the float bowl restricting flow into the float chamber causing fuel starvation after a run. If you leave the fuel pump running when the engine is switched off does any of the float bowls overflow, the smell of fuel would be a give away. I’ve had this problem before and a quick clean sorted the problem, your symptoms are exactly what I had!

 

[TimFZ]

Great stuff, will try those things. Remember the flat tops have an integral float with a little window which you can't see easily on the car. Will pump enough through to check there is no crud and flow check.

 

[Ian]

Sounds like my issue when I nought my car, which was coming from the fuel filter and further back than that it was from a dirty fuel tank.

 

[TimFZ]

So a thorough clean then from tank to carbs. What's the longterm solution, is it fuel tank out for clean or better filter / swirl pots just after? What filters do you recommend to prevent reoccurance?

 

[peter_s]

Great advice here, I would suggest a fuel supply issue as well. It can be the pump too, but a clogged filter would be a very high probability.

If it's coming from the tank I would take care of the problem at the cause, take the tank out and clean it.

 

[Rob Gaskin]

The easy answer is to buy a few filters and replace them regularly until it clears. If you have a rear electric pump put a filter before that - I did. If you don't the pump filter will need cleaning which is a chore.

 

[peter_s]

The easy answer is to buy a few filters and replace them regularly until it clears. If you have a rear electric pump put a filter before that - I did. If you don't the pump filter will need cleaning which is a chore.

Depends on what condition the tank is in. If it's bad you'll never get rid of the problem without cleaning it out and giving the metal some kind of surface treatment

 

[TimFZ]

OK, plan is to conduct a flow test near carbs. I would guess if the filter by the tank is blocked I will get an initial surge from the electric pump and then lower flow. Whilst doing this I will check for any debris on a filter paper in my receiving vessel.

Then I will change the rear fuel filter and see if this changes the flow, if it does, its the tank debris blocking the filter and lowering flow and dynamic pressure causing the problem.

I think the advice is good. I will get a large filter to replace mine and change regularly. I may even put in a small swirl pot to catch bigger stuff before the filter. It won't change pressure much and with a glass bottom I can keep an eye on any debris build up.

 

[Albrecht]

It's worth considering what might be inside your fuel hard lines too. The main feed from the tank to the front of the car is plated steel, and rust and other bits and pieces - usually coming from the tank - can make their way into the hard lines and get stuck. It reduces flow, sometimes getting dislodged enough to flow enough for normal running, then all the jigsaw puzzle pieces join together again and flow can almost stop altogether.

I've cut up old fuel hard lines and found all sorts inside them. The worst had what I would describe as shards of rust which had obviously been knocking around inside there for a long time, sometimes restricting flow and sometimes not.

So a good clear-out of the main fuel feed hard line can be a good idea.

 

[Farmer42]

The other thing to check is your points and condenser if you have a mechanical dizzy. They are prone to dying and it would give you similar symptoms to a fuel starvation.

 

[uk66fastback]

A good clear-out of the main fuel feed hard line can be a good idea.

What's the best way to do this?

 

[Albrecht]

What's the best way to do this?

I had some success with a length of old speedo drive cable, working from both ends (probably not getting all the way to the middle, but at least a fair bit of the way) and blowing through with compressed air afterwards.

Only way to be sure is to replace completely, which I've just done on one of my project cars and is a real P in the A...!

 

[uk66fastback]

Thanks. I cleared out the sunroof drain on my 944 with an old E string from one of my basses. Actually it was one of Status' - but I never told him ... (let's see if he bites)

It did the job pretty well.

 

[status]

Should’ve given you one of my Bs much thicker depending on gauge of course,let me know if you want anymore got loadsa time to restring all my basses ha ha

 

[TimFZ]

I got B strings on mine too, good idea! May fit additional large filter at front too then to stop anything reaching the pump. Thanks

 

[TimFZ]

OK, so, output from front electric pump is clean but there was a small swirl pot /debris collector between pump and carbs which was a bit blocked. Lots of black crap came out. Some carb cleaner and a shake later, all is clean and it is flowing freely an engine runs. Will be doing rear filter anyway to be sure...