Engine will only run above 4000 RPM. Carbs or timing?

[grannyknot]

Chris,

What is the #1 plug wire in relation to where the rotor is at TDC-that's what I want to see. Is the #1 plug wire lined-up with the rotor???? You never said whether you removed plug wires from the dizzy in all this process of swapping.

I think you seen that it isn't carburation -it's something else. It's ignition-timing or malfunction of spark.

After watching your video-all I can say WEIRD, and that sucks.

I am definetly scratching my head.

The raised mark on the side of the number 1 post on the distributor cap coresponses with the red marker I put on the distributor housing. "is the #1 plug wire lined up with the rotor" yes and no, the last pic shows the rotor centre just past the red maker, so to my understanding, the spark has fired just before the piston reaches TDC , the flame front expands and as the piston reaches TDC the combustion pressure reaches the maximum and pushes the piston down.

Oh, I removed the wires several times and I continue to trace my finger along every spark plug wire before every new attempt to get it going.

I made those videos so that hopefully someone will say "just do ... and your problem will be solved and also to prove that I'm not trolling.

What happens if you retard your timing a few degrees?

If by retard you mean turn the distributor CCW then it just won't start at all, at full CW (clockwise) the engine races. IF I HAVE THIS BACKWARDS SOMEOME PLEASE TELL ME. At the making of those vids the distributor is just a degree or so CW of the centre mark. Edited May 5, 2013 by grannyknot

[madkaw]

okay, if the #1 plug wire is lined up with mark on the cap, then you should be good as far as timing.

need to do more thinking...

[EuroDat]

I thought it was time to go back to basics, with the #1 piston at top dead centre this is what I'm seeing,

Is this 10 degrees off or bang on?

[ATTACH=CONFIG]63202[/ATTACH]

Cam lobes look right

[ATTACH=CONFIG]63203[/ATTACH]

Im wondering if the pulley hasnt slipped and the 10deg your reading isnt right. Mine slipped and I discovered it after tuning the engine. I checked it by punching the guts out of an old spark plug and welding a 6mm bolt in it. The bolt was just long enough to stop nr. 1 going over TDC (turning engine by hand), marked the pulley, removed the plug, turned engine just past TDC and repeated the procedure. Between the two marks is exact TDC. Mine was about 6deg out. The rubber insulator had slipped. It had me fiddling around a while before I found it. Would make it interesting if you was doing valve timing.

everything the same except now I'm temped to take a sledge hammer to this POS and teach it lesson.

Chris

I can completly understand your frustration. We are on the side line offering advice and your in the thick of it.

It might be time to walk away, relax and think about something else for a while and come back with a clear head. Better than freaking out and attacking the car, which you would regret. Its been such a good project so far. You just found your snag at the very end.

Gooluck

Chas

Edited May 5, 2013 by EuroDat

[bartsscooterservice]

Forget timing marks, pull the nr 1 plug, put a small screwdriver in the hole, and rotate the crankshaft cw with a ratchet and 27mm socket, look at the cam lobes to determine TDC, and you can feel with the small screwdriver the piston stopping for a moment @ TDC, stop there. The mark TDC with a dot of paint on the pulley, and recheck the distributor timing for nr 1. If that's all okay, the problem is somewhere else.

The engine revs going up an down, is that without touching the throttle?

[bartsscooterservice]

I still think it's carbs though...

I found this topic, looks similiar problem:

Engine revs up then dies upon starting within seconds - 521 - Ratsun Forums

How much pressure and fuel rate is the stock fuel pump giving and your RX7 pump? I would try a stock mechanical fuel pump, and clean the SU's again, use new gaskets, torque everything tight, and try again.

[madkaw]

It's almost impossible to think that both sets of carbs did the same thing.

[grannyknot]

So, I removed the damper/pulley today and put it on top of the pulley from the 2.4L, identical, same angle difference between the key way and the timing notch, so no slippage.

Rigged up this dial gauge/spark plug holder to verify TDC

With #1 piston at true TDC this is where the pulley sits,

The oil pump shaft is where it should be and the distributor is in perfect position.

I'm ruling possible timing issues out from here on, I've explored them extensively and it all seems to be in order.

Carburation, seems highly unlikely that two completely different types of working carbs could exhibit the same fault (however I still can't explain the high revs) but I'm going to put the carbs aside for the moment and concentrate on electrical, maybe I should try a set of points?

Is there any chance an open block breather could cause this? I know on FI engines it could play havoc.

Grasping at straws.

[madkaw]

Chris,

You have eliminated any possiblities of vacuum leaks?

Brake booster is disconnected -right?

No-having the crank breather shouldn't cause anything.

Wouldn't want to take some pics of your engine bay the way she sits now.

[grannyknot]

Madkaw, can't think where those vacuum leaks would be, every bolt is tight. Manifold to block, carb/spacer/manifold, and balance tube/manifold, I even plugged the coolant heating tube that goes through the intake manifold.

Here are some pics of the engine bay, good idea, maybe I'm looking at the problem without knowing it.

Fuel regulator set at 3.5 psi, I tested the fuel pump it is putting out 1.5 Litres per min.

[grannyknot]

I still think it's carbs though...

I found this topic, looks similiar problem:

Engine revs up then dies upon starting within seconds - 521 - Ratsun Forums

How much pressure and fuel rate is the stock fuel pump giving and your RX7 pump? I would try a stock mechanical fuel pump, and clean the SU's again, use new gaskets, torque everything tight, and try again.

Thru the regulator set at 3.5 I'm getting 1.5 Litres per min(I tested it with a jug and stop watch).

Fuel flowed at a nice steady stream. All bolts are tight.

If I take this to a shop to fix they are going to rape me and I'm not sure they are going to figure out either.

I've checked every system a dozen times. How does an engine pull enough fuel out of a carb to race it up to 4-5000rpm without touching the pedal?

Edited May 6, 2013 by grannyknot

[Wade Nelson]

Have you considered putting a vacuum gauge on it, to see if you have any valve damage, or running it on ether, to see if it's a carb problem?

[grannyknot]

Wade, have a look at these vids I posted in #77 or there abouts,

Vaccuum Reading L28 #1 - YouTube

Vaccuum Reading L28 #2 - YouTube

Ever since you posted about the vacuum gauge I've had one on at every attempt.

When I can get the engine to run at 4000 rpm with the help of the gas pedal the needle bounces like scenerio 3 in the vacuum website http://www.secondchancegarage.com/public/186.cfm

Edited May 7, 2013 by grannyknot