We Have Ignition - No Liftoff

[Mickey Richaud]

Tried to start the B at long last, after my rebuild attempt. I got 75 lbs. oil pressure cranking without plugs in - happy about that /ubbthreads/images/graemlins/laugh.gif

Then I hooked everything up to start it, and there's fire to the plugs, but no go. Gas is getting to the carbs (both of them), but on pulling the number 1 spark plug, found it dry. Also, while cranking, there doesn't seem to be any suction at the carbs. Seems like there should be. Decided to call it a day and maybe try again tomorrow. Any ideas on where to go from here?

Mickey

 

[Jim 67B]

Check the compression. If the compression is good check the timing, might be 180 out and if not check the floats in the carbs.

 

[Mickey Richaud]

Here's the latest: Compression is good - all four between 155 and 165. Ignition performing as it should - got spark at all four plugs. I pulled the drive gear for the distributor to make sure I had put it in correctly - no problem there. Pulled the carbs - plenty of fuel in the bowls. Checked the floats - both were a little off, so I corrected them. Jets are positioned right.

Still will not start. It did fire very briefly one time, but didn't run.

Any suggestions?

Mickey

 

[Bugeye58]

Mickey, did you verify the base static timing, and the plug wire sequence?
Jeff

 

[Mickey Richaud]

Hey Jeff -

When #1 is at TDC, the rotor is pointing to the number 1 terminal. Sequence is 1-3-4-2, right?

Mickey

 

[Bugeye58]

Mickey, that is correct, and I apologize for asking a stupid question. 1-3-4-2 is the firing order, and the rotor spins counter clockwise. Sometimes the obvious things get overlooked. If I may be permitted one more indulgence, are you sure that #1 is at TDC on the compression stroke?
I really <u>am</u> trying to be of assistance! /ubbthreads/images/graemlins/grin.gif
Jeff

 

[Mickey Richaud]

Appreciate it, Jeff - I'm notorious for overlooking the obvious (just ask my wife!).

Everything checks out. Guess it's down to cam timing, though I'm sure I assembled it with the proper orientation.

Mickey

 

[Bugeye58]

Mickey, when you assembled it, did you degree the cam, or just line up the marks?
Jeff

 

[Mickey Richaud]

Lined 'em up - don't have a degree wheel.

Since I'm at this point, what's the easiest way to check cam timing, short of pulling the radiator to get at the timing cover? I noticed Nial's post in the Spridget section about rotation of the crank after #1 is at TDC, but not sure I'm with him. He said one rotation, and the exhaust valve should be open. Mine is closed at one rotation.

 

[Bugeye58]

Mickey, it sounds as though you have the distributor drive spindle in 180 out. Both valves should be closed with #1 at TDC on the compression stroke, and both valves on #4 will be partially open. Rotating the engine 1 full turn should have the #1 ex. valve open when the piston is at TDC.
With #1 TDC, compression stroke, the slot on the spindle should be at approximately the 20 minutes until 2 o'clock position, with the large portion of the offset on top. I would think this is a better possibility than the cam timing being off.
I've got an engine on the stand right now, with the head off, and I'll go out tomorrow and verify all of this, and let you know.
Jeff

 

[Mickey Richaud]

Thanks, Jeff -

I'm calling it a day myself. I'm going to work on it tomorrow and see what develops.

 

[Bugeye58]

OK, Mickey, here's what I found this morning.
#1 @ TDC, compression stroke, both valves fully closed, the drive spindle located at twenty minutes to two o"clock, with the large offset on top. Distributor rotor pointed at about the same clock position for #1. Both valves on #4 slightly open.
One complete revolution, both valves on #1 slightly open, probably .150" or so, but you should have tension on both.
#4 valves fully closed, rotor 180 degrees from previous position.
If all this checks out, it verifies your cam timing and distributor installation. I would then try rotating the distributor while cranking, and see if you can get the thing to kick off.
Of course, I could always use a trip to Tennessee! /ubbthreads/images/graemlins/grin.gif
Jeff

 

[Mickey Richaud]

All right, Jeff! Thanks much. I'll check this out this afternoon, after I finish my lawn duty! I'll let you know what I find later.

Mickey

 

[Mickey Richaud]

OK - I know it's got to be something really simple, and I'm going to feel like an idiot (used to that!) whenever I get it right. The timing checks out. I've got good spark. I'm still not sure of the carbs. Although I rebuilt them, I did take them down again yesterday to reset the floats and reposition the jets (they were both too low, as were the floats). There is a bit of gas in the throats after cranking, but on the whole pretty dry.

The other question I have is this: When cranking, shouldn't there be some suction at the air horns of the carbs? I don't feel much (if any). If so, what does that indicate - valves not opening enough? Thought I'd set them correctly, and I did watch the valve train while cranking, and all seems OK.

Jeff - if you want to come to Tennessee, there's a bunch from Detroit coming to the Nashville show on Oct. 9 - Little British Car Co. inluded. /ubbthreads/images/graemlins/wink.gif

Mickey

 

[Bugeye58]

OK, Mickey, last resort. Spray some carb cleaner down the throat of both carbs, and see what happens. If it takes off, then dies, that indicates a fuel delivery problem.
Did you replace the jets? I've seen them where the little 'O' ring gets dislodged, and blocks fuel from entering the jet. (Rare) Quick way to check that is pull the suction chamber and piston, turn the pump on, and see if you can see fuel rising in the jet itself. You may also want to check that all the carb mount bolts, and intake bolts are tight. I suppose a massive vacuum leak would cause it not to inhale fuel.
I'm about out of ideas on this one! /ubbthreads/images/graemlins/confused.gif
Wish I could come down for the show, but that's my last race weekend of the year, and I have to drive my former car one last time. /ubbthreads/images/graemlins/frown.gif
Now I have to go finish the "oil change from heck" on my '72 Midget. I'll check back later.
Jeff

 

[Mickey Richaud]

Pulled the piston and chamber, and switched on the fuel pump. No gas rising in the jet. Yes, the pump is working - clicks away until it meets resistance. I did change the jets, but noticed there's a different jet listed for front and rear. I don't remember (been a while) how I put these back together. Which way should the pickup tube point? That's the only difference I see in the two. Also, what o-ring were you referring to regarding the jets? I don't have one, and don't see one on the exploded diagram.

Have to leave town for the week tomorrow. And, I have to order new seals for the fuel bowl cover. Ever notice when you pull the cover, those seals magically expand to the point where they're completely useless? All this will have to wait a while - it'll give me time to ponder the mysteries of the universe. They're a lot easier to ponder than this!

Mickey

 

[Bugeye58]

Mickey, the "O" ring I was referring to is on the HS4 carbs. You have the HIF's, don't you. I don't know the proper orientation for the pickup tubes for those, and I don't have a set handy here to look at. I'm sure Tony could tell you.
But, it definitely sounds like a fuel delivery issue.
Maybe the MGB elves will come and fix it while you are gone. /ubbthreads/images/graemlins/grin.gif
Jeff

 

[lawguy]

[edit] sorry, didn't see some of the later posts,

anyhoo, sounds like you are on the right track.

 

[Mickey Richaud]

Had to go out to Washington State due to death in family, and just got back last night. I plan to get back to the carbs this evening, and hopefully figure this thing out.

As I said earlier, the floats check out, the jets are new and everything is clean. Gas is getting to the carbs, but when the fuel pump is on, does not rise through the jet opening. Any suggestions there?

Also, what about the "starter valves" in the carbs? Anyone know their purpose and how they work? I'm wondering if the problem might be with them.

Mickey

 

[Mickey Richaud]

SUCCESS! (Sort of...)

Pulled the carbs apart once more, and replaced o-rings in the starter valves. Put everything back together, and she fired up. Ran for about 30 seconds, then quit. I played around with it for another hour or so, but no luck. When running, I noticed well over 50 lbs. of oil pressure, and it sounded fine. A bit of backfiring through the carbs, but other than that, wasn't too bad. Apparently still have a problem with fuel delivery, so I'll have to play around with the carbs some more.

Unfortunately, it will have to wait until after the show in Franklin (Tenn.) this weekend. Hope some of you can join us - looks like it will be a nice show.

Mickey