need help -- hesitation and back fire (1 Viewer)

[2fpower]

facts:

1968 landcruiser, ol' blue. here is thread:

Ol' Blue, my 68' fj40 project

original f engine. electronic distributor from @Trollhole Carb was just rebuilt by @FJ40Jim

SD40 aisin carb, small sight glass (round showing)

symptom.

Car idles great and starts great after jim rebuilt the carb. Night and day difference!!

Under load, when I start driving, it starts hesitating is the issue.

My thoughts are timing or carb fuel issues, but don't know how to check either.

The timing marks are not visable, so one of the question is, how do I time the engine by ear, not using the timing marks/light?

 

[FJ40Jim]

Make timing marks if you have to. Remove #1 plug, turn engine by hand, feel in hole with screwdriver for piston to top out at TDC. Make a mark on FW in timing hole for TDC. Use adjustable timing light to set base timing.

 

[2fpower]

Make timing marks if you have to. Remove #1 plug, turn engine by hand, feel in hole with screwdriver for piston to top out at TDC. Make a mark on FW in timing hole for TDC. Use adjustable timing light to set base timing.

Brilliant! Thanks

 

[65swb45]

Brilliant! Thanks

You should see him on a good day!

Chances are good if you pull off the inspection cover and run a wire brush around the front face of the flywheel, you will find the marks.

X2 on Investing in an adjustable timing light if you don't already own one.

 

[Pin_Head]

Could be more than one problem.. Backfiring through the carb is a fuel starvation issue.

 

[2fpower]

Come on @Pin_Head let me dream that it just timing.....

 

[Monty231]

It could be that the secondary is opening slightly via the mechanical linkage, but not enough for the vacuum to open it fully. This would cause it to lean out from the extra air in the secondary. You can test it to see if it is opening with a paperclip. If it isn't opening all the way there is an adjustment on the linkage.

 

[FJ40Jim]

It's a D40 1bbl carb, no secondary barrel to adjust.

 

[YukonCruisers]

Have you replaced the coil? My coil went and I thought it was a timing issue - would start fine, drive for a mile or so, then backfire through carb and then not start until coil cooled...

 

[CHCP]

Could be more than one problem.. Backfiring through the carb is a fuel starvation issue.

I had a similar problem with a 78 2F and 2 barrel Weber. Engine ran fine at idle and running on flats but the idle rpm changed once in a while always seemed to decrease when pulling up to a stop sign and nearly stalled. The truck would start to vibrate and backfire on hills and when loaded like with a trailer. I found that the fuel pump cam lever spring had come off its detente, not allowing the full throw of the pump lever. I'd think a good way to check this is to run your engine at a high rpm and making sure the fuel level in your SD40 doesn't change much. I have heard that worn fuel pump cams can cause the return spring problem.

 

[2fpower]

Have you replaced the coil? My coil went and I thought it was a timing issue - would start fine, drive for a mile or so, then backfire through carb and then not start until coil cooled...

Yes, new coil, and use electronic ignition from Trollhole.

 

[2fpower]

Just got back into town, so will check timing tomorrow and see how it does.

Thanks for advice.

 

[2fpower]

Timing marks were perfect OEM, and it was off quite a bit. Adjusted it and the hesitation is gone. Thanks everyone. I have a problem with the bowl continuing to fill after the car is turned off. I will shoot @FJ40Jim a PM to see what the fix is.

 

[2fpower]

Well, for some reason, I can't start a conversation, so we will do it here.

As I said, after I turn off the car, you can see through the fuel glass that the fuel level keeps increasing. If you try to start it a few minutes later, it is flooded and will not start. Wait 10 minutes, floor the car, and it eventually starts.

I put a new float and needle on it and I know you did the same thing, as you sent me my old (new) float back. Is there some pressure release modification, or something we can do?

Thanks,

 

[White Stripe]

I'm more familiar with American carbs, but typically their is a adjustment to set the float level

 

[thebigredrocker]

I think you are asking how to stop fuel from filling the bowl so full. You have to flip the air horn over and bend the center tab on the float. Push it closer to the needle. While you're in there, you might blow air through it.

I'd measure the float height before adjusting the tab. If you bend it too far this go-round you'll have data for the 4th time you go in for surgery on the float.

 

[FJ40Jim]

There should not be pressure in the fuel system after engine shutdown. There is a problem with tank venting. The high vapor pressure of RFG in a sealed gas tank is overcoming the needle & seat. Most likely is a later gas cap that is not vented, or the vent hole in cap is plugged with a spider nest.

 

[2fpower]

Thanks Jim.

Ok. Will look at the cap. It is original to the car.


To be clear, the float is adjusted fine. Fuel level is perfect when running. Issue is that there is some pressure that makes it overfill after the engine is turned off.

 

[Poser]

Ok. Will look at the cap. It is original to the car.

To be clear, the float is adjusted fine. Fuel level is perfect when running. Issue is that there is some pressure that makes it overfill after the engine is turned off.

So to be clear, you purchased this vehicle new, from Toyota back in the late 60s and the fuel cap has not ever been replaced, OR, it is the fuel cap that was on the vehicle when you purchased it from a previous owner?



When this situation is happening, remove the fuel cap and see if the situation persist, please.



The vented/non-vented cap scenario advice provided above is solid and has proven to be an issue with many a Land Cruiser.

 

[2fpower]

@Poser Why do I get so excited when I see that the great "POSER" has replied to something I typed???

You have a good point. It came with this car which was very much in original condition, and looks to be OEM, so I did assume.

Is there a replacement cap that looks original? Toyota still sell it?