2.4 twin plug, will not start..

[swade]

Folks,

Engine is in with higher comp pistons, twin plugged/port worked heads, twin MSD, JB Racing distributor. Using the PMO 40's that were on it from before (have not touched settings). It tries to start, but will not actually run after cranking is stopped. I have a remote start hooked up so that I can view the engine comparment while cranking

Suggestions welcome

So far checked:

All the plugs/wires go to the correct positions (checked 20 times)
CW rotation on the rotor
Fuel pressure 3.5 psi
Fuel flow checked after both side carb fuel filters +-2.4 l/m
Both MSDs LEDs flash while cranking and semi-running
Checked spark to all plugs with an inductive clamp, all getting spark
Checked the rotor is at #1 TDC
Rechecked my cam timing while I was in there and just as I set it at 4.5mm
Timing light shows timing at cranking near TDC

Thanks,

Wade

[Steve@Rennsport]

Hi Wade,

Wellsir,....these things will start when they have compression, properly timed spark, & fuel.

Acting under the main principle of NEVER, EVER assuming anything:

1) Install a spare plug into a connector and ground it to observe a nice fat, blue spark while cranking.

2) Remove an aircleaner to look down a throat and observe fuel being squirted from the accelerator pumps while actuating the throttle.

3) If you have a good spark (as above), and fuel discharges from the accelerator pump nozzles when the throttle is pumped, the only things left are incorrect ignition timing or valve timing. Since the engine is all brand new, it should have sufficient compression to start,...

Let me know what you find.

[T77911S]

BEAUTIFUL

it can only take 2 swapped cyclinders for it not to start. i jst did that on my 930. 2 and 3 swapped, it would barely run if at all.

check timing as far as when it fires. never tried it while cranking.

you can still have everything 180, although you usually get a good backfire with that.

rotor can be lined up to #1, crank at TDC but on the intake stroke(valve overlap) instead of power stroke.

[rsscotty]

The wires coming out of the JB distributor are orange and purple. The MSD wires are green and purple. Make sure the JB purple goes to the MSD green, and JB orange to MSD purple. It has all of this in the JB instructions but sometimes it is missed.

[swade]

Thanks for the replies all,

Steve,

Did the spare plug check and there is a good spark, I checked a plug on top and bottom of both banks (4 plugs).

The accelerator pump is squirting fine.

T77911S

I am certain of the plug wires being in the cap properly, have now checked again.

rsscotty

The MSD wires are as you described, checked again with the manual.



The engine is trying to start, but just has no ass and will not continue running.

Let's talk timing then. I plulled the valve covers off earlier today and the cam timing from #1 TDC was at 4.5mm on the left bank after turning 360 degrees, and after 720 degrees it was at 4.5 on the right bank as per specs.

When the #1 intake valve is closed and the Z1 mark lined up at the crankcase split the distributor is pointing at cyl #1

Open to suggestions or pointing out something I am missing,

Regards,

Wade

[T77911S]

did you put in bigger cams too? not sure how well an engine would run with high compression and stock cams?? dynamic compression could be very hi.

if you upped the compression and with or without bigger cams, the mixture could be off due to more air. richen the mixture 1/4 or 1/2 turn.

if still no go, i would consider a compression check.

[Steve@Rennsport]

OK,...thanks for those data points.

1) Fuel levels correct at the windows on each carb?

2) Remember now, these carbs have no starting chokes or cold enrichment devices: YOU are the one who does all those functions using your right foot & the accelerator pumps. Starting from cold, especially on the initial start before any adjustments) requires many pumps of the pedal to get sufficient fuel into the engine to start and stay running until warmed up a little.

It may take 10-15 pumps to get started and some foot action to stay running until youi can make all the throttle, idle mixture and idle air bypass adjustments.

[T77911S]

is it popping out of the carbs when it tries to run or is it like it has absolutely no power?

another thing, plugs can foul very easily with carbs.

[swade]

Folks,

I am sure it is not fuel related, plugs clean and the car was carbed before, a few pumps and feather the gas to get her going in the morning as Steve mentioned.

I just did a compression check and am surprised to find zero compression on 1-4 and +-150 on 5 & 6. I obviously have a cam timing problem even though (i thought) I followed the timing procedure, maybe I am 180 deg out on both sides? I hand cranked the engine many times after everything was together nothing hindered the rotation, and i timed the cams to the 4.5mm specs, and checked again.

Wade

[swade]

T77911S,

Not popping out the carbs but backfiring out the exhaust, plugs were clean.

Wade

[Rich Lambert]

Is the switched power input to the MSD(s) taken off the ignition "start" circuit? When I first installed mine I had it wired up so the MSD was powered on only when the key was turned to the start position. When I released the key, the power to the box would shut off. The engine was essentially running while I cranked it and then nothing. It was wired up per the MSD tach adapter instructions too. Check for (+) on the switched power input wire with the key in the "on" position.

[swade]

Rich,

Power to the MSD boxes comes from a switched 12V that stays on when key turned. I have a remote starter switch hooked up to activate the starter solenoid attached between the battery lead on the starter and the solenoid spade terminal.

Thanks,

Wade

[swade]

When I first posted this thread I had no idea that it would take so long to start-up my car...

After the rebuild in April and initial almost start, backfire through the exhaust, jumping and shuddering I checked compression and only had compression on two cylinders. I had to travel to Brazil for a couple of weeks on business so put everything on hold. I was pretty convinced that I had damaged something, I was pretty sure that my cam timing however was good so could not think of what was possibly wrong.

Upon return from Brazil I dropped the motor to put it on the stand to see what was going on. Checked cam timing, it was right on. So I pulled the top end to see if there was valve or piston damage, and found nothing wrong at all. Re-assembled the engine, re-installed it, checked all of my new ignition wiring, cleaned and sprayed though the carb passages to make sure, and the start-up problem was identical. Crap!

I spent the last couple of days troubleshooting with nothing found until this morning. The twin plug Hargitt lower valve covers are not as deep as the turbo valve covers that I was using prior to twin plugging the heads. I saw them for sale for a pretty reasonable price by a fellow Pelicanite and purchased them. Finally this morning I did a compression test with the valve covers off and had compression... suddenly. I looked on the inside of the valve covers and sure enough the clearance adjusting screws had been hitting the valve covers and not allowing the exhaust valves to close completely... at last a possible solution.

I relieved the valve cover material with a die grinder where the screws were hitting. I checked clearance with a couple layers of 0.5mm tape on each position and re-installed to see if they still hit, which the did not. Put everything back together AGAIN and she started right up, no hesitation, no popping, no backfiring. Did my run in, changed oil and filter and have already put 75km on the car today, what a gas.

See photo showing the Hargitt valve cover with the circled spots where the screws hit and a turbo valve cover above it. Enough typing, off for a drive.



W

[Jim Richards]

Great job troubleshooting the problem, Wade. Lower valve covers. Who would've thought...

[Tom '74 911]

Originally Posted by Jim Richards

Great job troubleshooting the problem, Wade. Lower valve covers. Who would've thought...

I'll second that! I'm not sure I would've ever thought in a million years to look at the lower valve covers as a possible source of a no-start issue. Even though it took some time and I'm sure caused you a lot of frustration and gray hairs, good troubleshooting!

I hope you get to enjoy your car for a long trouble free time!

[swade]

It felt like a million years to figure this out, believe me. After you drain your engine of 9L of oil, how can another 9L leak out on the floor below the engine stand?

[356RS]

Great job Swade. We all leaned something to watch out for. That's a new one for me.

[Steve@Rennsport]

Very well done, Sir.

A tip of the hat to you for persevering and finding an obscure problem (with a simple solution).

We usually use the OEM Turbo covers on earlier 911's and sometimes the Hargett ones on the 3.6 engines so I've not have this happen to me.

[bavaria911]

Fantastic bit of information for a newbie doing twin plug and gathering parts ahead of time. Lesson learned.

[m110]

wow...the best laid plans...

Thanks for sharing, someone else will avoid this, thus defining the beauty of this forum.

Please post a review of the engine once broken in!