Engine starting issues

[jfalesi]

Hey guys/gals. Just looking for some ideas... I've got a '71 Suburban with a new gas tank and we're trying to start it for the first time since installing the tank. Before the install, it was sitting for the better part of a year and wouldn't start. I diagnosed a leaky fuel tank and bad gas. I replaced the tank and all the rubber hoses. Today a friend came over to help me get it started. We verified that the distributor is on properly (I pulled it off to prime the oil pump), replaced all the plugs and wires, checked the plug order three times, verified that the dist and the crank were at #1 TDC, and primed the fuel line. We checked the spark with an in-line tester and verified spark. We disconnected the fuel hose at the carburetor and verified that we were getting gas from the pump. Then we cranked the engine a number of times, with a couple of different dist orientations, and only got backfiring (we had poured gas into the carb). We checked for gas from the fuel line to the carb again and this time saw nothing. So we're thinking it's the fuel pump. Any other ideas of what we should check?

FYI I've got a 350 crate engine and HEI. Yes, there's gas in the tank :-D

Thanks!

[Overdriven]

Clogged or kinked lines are possible and it would stink to replace the pump and still have an issue.

Verify you’re getting fuel to the fuel pump. I’ve had some vehicles that were very stubborn getting fuel to the pump after running out or replacing a component in the fuel system before the pump.

[Chris_oz]

Sounds like the distributor is one the wrong stroke.
Very easy to do.
How did you confirm that you were on the compression stoke on No 1?

[LockDoc]

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Even if the pump is not working it should still fire and run for a bit by pouring a small amount of gas in the carb. Is the choke open or closed when you try it.

Like Chris mentioned above, it is easy to get it timed on #6 instead of #1 and that would make it backfire.....

LockDoc

[franken]

I wonder if the accelerator pump is squirting. If not, no gas yet, or gummed up carb.

[AussieinNC]

Back to basics....
Remove the spark plug for cylinder #1...

Have an assistant bump the key while you have your thumb over the spark plug hole...

You will feel compression pressure start to build up in the cylinder...stop and turn off the key....

By hand , turn the crank pulley until the timing mark on the crank pulley is aligned with the 10 degree mark on the timing tab...

Remove the distributor cap...the rotor should be pointing at cyl #1 distributor cap post..if its not, rotate the distributor to get it to be lined up...

If it is not possible to align, remove the distributor and reinstall with correct clocking...

Most backfires occur when distributor is 180 ot of phase...firing 6 instead of 1...

Let us know how you go...

[jfalesi]

Originally Posted by Chris_oz

Sounds like the distributor is one the wrong stroke.
Very easy to do.
How did you confirm that you were on the compression stoke on No 1?

Timing tab on the flywheel and finger in the spark plug hole.

[jfalesi]

Originally Posted by LockDoc

-
Even if the pump is not working it should still fire and run for a bit by pouring a small amount of gas in the carb. Is the choke open or closed when you try it.

Like Chris mentioned above, it is easy to get it timed on #6 instead of #1 and that would make it backfire.....

LockDoc

Not sure about the choke - my friend was jiggering the throttle on the carb while I was cranking the engine.

[jfalesi]

Originally Posted by AussieinNC

Back to basics....
Remove the spark plug for cylinder #1...

Have an assistant bump the key while you have your thumb over the spark plug hole...

You will feel compression pressure start to build up in the cylinder...stop and turn off the key....

By hand , turn the crank pulley until the timing mark on the crank pulley is aligned with the 10 degree mark on the timing tab...

Remove the distributor cap...the rotor should be pointing at cyl #1 distributor cap post..if its not, rotate the distributor to get it to be lined up...

If it is not possible to align, remove the distributor and reinstall with correct clocking...

Most backfires occur when distributor is 180 ot of phase...firing 6 instead of 1...

Let us know how you go...

Yeah, that's what we did. It was a while ago, but I went through that procedure and my friend verified that it was at #1 TDC. I guess we could both be wrong.

[jfalesi]

Originally Posted by franken

I wonder if the accelerator pump is squirting. If not, no gas yet, or gummed up carb.

Not sure. I wasn't pumping the accel, but my friend was operating the throttle by hand on the carb.

Carb could be gummed. I have some carb cleaner...

[jfalesi]

Originally Posted by Overdriven

Clogged or kinked lines are possible and it would stink to replace the pump and still have an issue.

Verify you’re getting fuel to the fuel pump. I’ve had some vehicles that were very stubborn getting fuel to the pump after running out or replacing a component in the fuel system before the pump.

We did prime the fuel line (buddy sucked on the line, I teased him about it) and there was fuel at the pump at one point. After trying to start it for a while, and then letting it sit in case it was flooded, we cranked it a couple more times and didn't see any gas at the pump.

[Chris_oz]

Originally Posted by jfalesi

Timing tab on the flywheel and finger in the spark plug hole.

Backfiring confirms you have 2 things, Fuel and spark, just not at the right time.

you will get some compression on the exhaust stroke too, as the exhaust valve is only just beginning to open when the piston is heading up on the exhaust stroke.

If you take of the rocker cover, you can confirm you have a closing intake valve as the timing mark for no 1 is coming up, if you have movement at the exhaust valve, you are 360 out on the crank and need to go around another full turn of the crank

once you have the timing mark on 10 deg btdc No 1 COMPRESSION stroke, take of the dizzy cap, ensure its pointing towards No 1 lead.

If its 180deg out, you can redo the leads as a quick fix, or retime the dizzy, normally the rotor button will point towards no1, but you can set it where ever you like, as long as the cap and leads line up with it.

I have seen people driven to despair by this, flooding engines, destroying starters, new cams and batteries trying to get them to fire.

if you have the spark 10 deg BTDC on the correct stroke, pour fuel down the carby...it will run.

[LockDoc]

Originally Posted by jfalesi

Not sure about the choke - my friend was jiggering the throttle on the carb while I was cranking the engine.

If you are pouring a small amount of fuel in the carb you will probably have to close the choke to start it or it will get too much air for the amount of fuel making it to the cylinders.

LockDoc

[jfalesi]

Originally Posted by Chris_oz

Backfiring confirms you have 2 things, Fuel and spark, just not at the right time.

you will get some compression on the exhaust stroke too, as the exhaust valve is only just beginning to open when the piston is heading up on the exhaust stroke.

If you take of the rocker cover, you can confirm you have a closing intake valve as the timing mark for no 1 is coming up, if you have movement at the exhaust valve, you are 360 out on the crank and need to go around another full turn of the crank

once you have the timing mark on 10 deg btdc No 1 COMPRESSION stroke, take of the dizzy cap, ensure its pointing towards No 1 lead.

If its 180deg out, you can redo the leads as a quick fix, or retime the dizzy, normally the rotor button will point towards no1, but you can set it where ever you like, as long as the cap and leads line up with it.

I have seen people driven to despair by this, flooding engines, destroying starters, new cams and batteries trying to get them to fire.

if you have the spark 10 deg BTDC on the correct stroke, pour fuel down the carby...it will run.

I did all that... I had both valve covers off and verified that the correct valve was opening. It's possible that I got it wrong - it was the first time I had ever done it, and it was a while ago. If it comes down to it, we'll pull the valve covers off and re-do it.

[jfalesi]

Originally Posted by LockDoc

If you are pouring a small amount of fuel in the carb you will probably have to close the choke to start it or it will get too much air for the amount of fuel making it to the cylinders.

LockDoc

How do you close the choke? Pump the accelerator? Is that something my buddy may have done when he was operating the throttle at the carb?

[Chris_oz]

Originally Posted by jfalesi

I did all that... I had both valve covers off and verified that the correct valve was opening. It's possible that I got it wrong - it was the first time I had ever done it, and it was a while ago. If it comes down to it, we'll pull the valve covers off and re-do it.

You should not have a valve opening, the intake should almost be closed almost 180 degree before tdc.
If yhad a valve opening, it was the exhaust and you are on the wrong stroke.
Each time the mark on the balancer comes to tdc, no1 is up the top, but it does it twice for each firing cycle.

Double check the dizzy before you spend too much time on the carby.
It will run without a carby if you pour fuel down its neck and crank with the timing right.

[LockDoc]

Originally Posted by jfalesi

How do you close the choke? Pump the accelerator? Is that something my buddy may have done when he was operating the throttle at the carb?

With the throttle part way open you should be able to close it by hand. If the engine is cold it should actually close by itself when you open the throttle all the way.

LockDoc