Engine fires but wont keep running

[StewRat]

Happy new year peeps!

Quick recap - got the Stew Rat firing for the first time in late October, but on second firing bent 2 push rods.
Took the top end apart and then had to park things while we did some work on the house, and then Xmas.

With that out of the way, I got back into it last week with new pushrods (reckon a beefy rocker cover may have been the culprit).

Had a problem getting all cylinders to fire but that is sorted now.

Problem I have is that I can get the engine to fire after a few squirts from the pump jets, and can just about keep it going if I keep squirting with the right cadence, but it wont keep running on any throttle position after (it feels like) the pump jet gas has been used up.

I've checked good flow of fuel from the regulator to the carbs.
All barrels squirt on the pump jets so the fuel is getting that far.

Can I get some advice on the right next step on fault finding/diagnosis?

Should I be tracing the fuel flow through the carbs (dual DRLA 40s)? Mixture screws are the recommended 3 turns (and have tried 3.5 turns) out.

All the diagnostics I see about settings, jetting etc are based on the engine running, however roughly, but I'm not getting to that point.

Please help me take a step back and work out what is going on.

Thanks

Stewart

[Garrick Clark]

If you have fuel squirting out the accel jets my diagnosis is spark related.
What type of ignition you using

[Chip]

If you have fuel squirting out the accel jets my diagnosis is spark related.
What type of ignition you using

Other than the fact that it does keep running as long as he is pumping the throttle. You have carb issues.

[spanners]

It must have spark to run as it does, so not enough fuel or not able to suck it in, IE manifold air leaks, but just quickly loosen off all the idle jet holders 1/2 turn and try it. if it runs now the idles are either too small or blocked. genaraly, more info is needed, bent pushrods may mean other damage so how did that happen?

[stussyrich]

clean the carbs properly with an air line and check the timing.

[RMS Boxer Service]

How old is the fuel?? Fuel now a days would'nt last long and makes a high performance engine run  strangely or not at all.

/Rolf

[StewRat]

Thanks for all the suggestions

Ignition is MSD 6-AL, with flame thrower/pertronix distributor and MSD coil. I did a bunch of lead/plug checking when it was only firing on 3 cylinders so I'm now fairly sure they all have a good spark.
Would it run on pump jets if spark was poor/missing?

Fuel is new - filter before the pump.

Fuel supply - I dont have the calcs here, but I timed the output from the regulator into a jug and checked with the figures in the Dellorto book for a 2276 @ 6000rpm and supply is comfortably over requirements.

Loosening idle jets - great tip, but didn't change anything.

Timing - is currently 10 deg static. Cant do anything else without it running continuously.
When it runs on a good shot of fuel - albeit for a second or 2 - it does sound "right", even, barping nicely, would it do that with really bad timing?

Seems like I need to a) check the floats to make sure they are keeping the supply topped up and b) re-clean everything.

So near yet so far - as I mentioned in a VWDRC post on FB, if I can get my reaction time down to 0 and an ET of 1 second, the Stew Rat is good to go!

[richie]

From what info you have written[and its always going to be hard to diagnose this way] it sounds like it is really retarded to me on timing. When it is a lot retarded it wont really want to run on its own but will just about when forced, How did you manage to check it has 10 degrees static timing? Any chance distributor drive is tooth out?

 Have you tried putting some more turns in idle screws so it should idle quicker and see if it will run with out keep stabbing throttle.

Are you sure it actually runs on all 4 cylinders? laser temp gun is best for this after you run it for few seconds, but you can also touch header carefully   on each tube few inches from heads after running it

Is it possible you could get someone to video it while you start and run it and share it so we can see & hear what is happening?

cheers Richie

[StewRat]

Hi Richie

I do appreciate this is not ideal for diagnosis - just happy to get pointers for avenues to explore.

Pretty sure it is running on all 4 - it wasnt originally, which I discovered by touching the header tubes. With this running duration they're not scalding hot, but cold really stood out.
Now even after a few short bursts I can at least check that all tubes are the same temp.

I'm pretty sure the extra idling screw wont help as no intermediate throttle does - but I will check.

 Timing is worth me exploring further. It has been a bit of a black art so far. Your description of "a lot retarded" makes me wonder if I am far out.
My current 10 deg assertion is based on finding TDC with #1 valves both closed, positioning the graduated pulley to 10 deg BTDC and rotating the distributor using the LED on the MSD box to indicate contact.. 
It is worth noting that the #1 lead using that process is not in the 5 o'clock position I see referred to (Its a bit north of that) , so it is possible I dropped the dizzy in a tooth out. But ... regardless of where it physically is, I *think* that doesn't matter as long as the index point is right? Maybe I should pull that and re-install.

I'm sure I can tape my phone somewhere to record this to let you see ...

Thanks again to all.

Stewart

[spanners]

you turned the dizzy the right way? ie anti clock, or in other words against the rotor arm rotation?

[StewRat]

you turned the dizzy the right way? ie anti clock, or in other words against the rotor arm rotation?

Yes - but I'm now tempted to try again at 90 degree intervals just to make sure I've covered all the possibilities.

[spanners]

explain those bent pushrods please, what cylinders and what valves. i suspect no suck which explains firing on pump squirts only, get an aerosol can of wd40 to hand and fire it again having loaded wd40 all round the intake flanges both banks, if it keeps running as you load the flanges with wd you have intake air leaks, what happens is the wd gets sucked in at the leak area and fires the cylinder untill the wd runs dry again and it then sucks just air.

[StewRat]

It was the timing. Bit of trial and error but advancing it more and more until it fired up easy and kept running with progressive throttle response.
Sounds ok I think?
http://stewrat.stewarthutton.co.uk/wp-content/uploads/2017/01/Jan_2017_start.mp4

Need to get a muffler for tuning in the lockup I think. Guy from across the road came out to see if I was finished as apparently his kid was "shiting himself". To be fair, it was nearly 10 o'clock by then.

Thanks for all the help.

@Spanners - to close the loop, the bent pushrods were on #2, exhaust worse than inlet. I couldn't find any cause other than dings inside the rocker cover that suggested it was too thick/close. Having rebuilt the rockers (with I think fewer shims) and grinding out the covers, all seems good now. No doubt lots of room for improvement and tightening up on things but first objective was to get it running - and I was failing at that until tonight!

[Garrick Clark]

Glad you got your spark related timing issue sorted ;

[richie]

Cool, get a timing light on it straight away and check its close now

[StewRat]

@ GARRICK.CLARK   

@ Richie - will do. Timing gun is ready n waiting,.  Lots of tuning and stuff to do now it is actually running and I dont need to be in the cockpit pumping fuel.

90% done, only the other 90% left to do ...