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74.5 MGB Will Not Start

Posted by 1MGBOCD 
1MGBOCD Avatar
Michael James
Mesa, Arizona, USA   usa
1972 MG MGB "The "Brit Pit""

This Halloween I dressed as a “Bad Mechanic!” I wore the costume all weekend as I tried to figure out why my recently acquired ‘74 MGB would not start. I truly lived up to the spirit of the costume as I completed the following:
• Flushed the year-old gas from the tank
• Allowed the fuel pump to push the gas to the engine compartment and
into a bucket (successful fuel pump test)
• Disconnected the fuel line at the pump and blew air through the line
to the engine compartment (not into carbs)
• Now has 5 new gallons of gas
• Changed the fuel filter
• Removed the SU carbs
• Cleaned the healthy buildup of sediment from the bottom plate of each
• Removed the pots to verify needles moved freely
• Reinstalled the carbs with new gaskets
• Removed the distributor
• Gapped and installed new points
• Installed new condenser
• Installed new rotor
• Reinstalled same distributor
• Static-set timing
• Confirmed wire is attached to the distributor
• Installed new distributor cap
• Gapped and installed new plugs
• Installed new wires
• Tested coil (good spark from coil while held to engine block)
• Tested all plugs against the block and have a good spark at each. None were
wet, all smelled of gas
• Cleaned the leads to the battery and where it grounds to chassis

At this point let me just say that I could have accomplished NONE of this without the plethora of information found on this forum. Thanks to so many of you who have contributed with articles, repeatedly answered the same questions over and over and patently guided the non-mechanical to victory over these dang LBC’s

After all this, the car still will not start. The battery is strong and turns the engine but it refuses to fire. I’ve tried choke on, choke off, choke halfway, choke wife, spraying starter fluid directly into the carbs, closing my eyes and pleading, cussing, throwing tools. Nothing seems to work. I even noticed the gas cap does not fit snuggly, so I held that firmly in place while a helper tried to start the car. Nada. The car only cranks over and over but does not start.

My next direction is to rebuild the carbs but since started fluid does nothing, I’m not sure it’s a necessity. I will pick up a compression gauge tonight to check combustion but I’ve heard even with poor compression the car should start. The good news is that I have to other B's to steal parts from as necessry

Hopefully someone out there is still wearing their Superman-chanic costume and can offer more suggestions. I am at work today so if pics or more info is required, I will comply as soon s possible. Thanks guys, in advance. You have already been a huge help in my troubleshooting. MJ
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pburchins Avatar
Patrick B
Atlanta, GA, USA   usa
1976 MG MGB "Spalding"

I am going to be doing the exact same thing that you are doing right now next weekend. LOL, at least you have your sense of humor! Best of luck !
dickmoritz Avatar
Dick Moritz
Philly 'burbs, PA, USA   usa

Michael,

I suspect you're assuming that the firing order at the distributor cap was correct. If you haven't already done so, I suggest that you confirm firing TDC at #1 cylinder, either by turning the engine slowly with the #1 plug out and continuing past compression to where the timing marks line up or, alternately, removing the valve cover and slowly turning the engine until #1 intake valve opens and closes and lining up the timing marks at the balancer. Then note the position of the rotor and put #1 plug wire at that location, with remaining firing order 1-3-4-2 counterclockwise. Possibly the PO attempted a tune-up and could never get it started again, which would explain why it found its way into your garage... winking smiley

And if that doesn't work, compression test?

Dick



Errabundi Saepe, Semper Certi
(Often wrong, but always certain)
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1MGBOCD Avatar
Michael James
Mesa, Arizona, USA   usa
1972 MG MGB "The "Brit Pit""

Forgot to mention, long before I replaced or changed anything, the car started and ran for about 6 seconds then begam to sputter so I reached in and pulled the choke out a little. The car died immediately and has not started since. Also, it backfires and sprays gas/air from the carbs when trying to start.

Confirmed firing order is correct
dickmoritz Avatar
Dick Moritz
Philly 'burbs, PA, USA   usa

In reply to a post by 1MGBOCD Forgot to mention, long before I replaced or changed anything, the car started and ran for about 6 seconds then begam to sputter so I reached in and pulled the choke out a little. The car died immediately and has not started since. Also, it backfires and sprays gas/air from the carbs when trying to start.

Michael,

Backfire is usually an ignition/timing issue, so you may want to triple-check ignition system. Also, since you ran the car on very stale gas, pull the valve cover to inspect valve action and also do a compression check. It's possible that the stale gas turned to varnish that has possibly burned onto one or more valve stems, holding the valve(s) open.

Dick



Errabundi Saepe, Semper Certi
(Often wrong, but always certain)
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abstractduk Avatar
neil aldridge
London, United Kingdom   gbr

i would advance the timing by slight increments until it catches-in my short experience, a low compression engine should kick over and fire easier than a high compression engine, so i wouldnt put so much focus on it. its gotta be a timing or firing order issue..if advancing the timing doesnt work id go with dicks suggestion that it might be firing on the wrong cylinders.
MaddogSprite3 Avatar
jeff rohrbach
raleigh nc, USA   usa

Michael, shot in the dark here, but you did make sure you didn't reverse the cogs on the distributor when you re-installed? Also, contact points, lead wire from condendsor has to be on the correct side of insulator. Could lead to problems if not. Hope you get it runnin. Let us know, please!
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1MGBOCD Avatar
Michael James
Mesa, Arizona, USA   usa
1972 MG MGB "The "Brit Pit""

Thanks all. I will try these suggestions this week and give a status.
1MGBOCD Avatar
Michael James
Mesa, Arizona, USA   usa
1972 MG MGB "The "Brit Pit""

Ok, here is a quick status

[/quote]
Michael,
Backfire is usually an ignition/timing issue, so you may want to triple-check ignition system. Also, since you ran the car on very stale gas, pull the valve cover to inspect valve action and also do a compression check. It's possible that the stale gas turned to varnish that has possibly burned onto one or more valve stems, holding the valve(s) open.
Dick[/quote]

I currently have the valve cover off and can see all cylinders are moving as I crank the motor. Have yet to try compression check


In reply to a post by MaddogSprite3 Michael, shot in the dark here, but you did make sure you didn't reverse the cogs on the distributor when you re-installed? Also, contact points, lead wire from condendsor has to be on the correct side of insulator. Could lead to problems if not. Hope you get it runnin. Let us know, please!

Not sure what a "cog" is on the distributor but I am positive I replaced the distributor the same way it was removed. Had to fiddle with the rotor to align but when completed the rotor arm was pointed at #1 position and cylinder #1 at 10BTDC
Condensor is installed correctly. Both wires together above the points adjustment arm. No upper insulating washer required on top portion of PLASTIC bolt.


In reply to a post by abstractduk i would advance the timing by slight increments until it catches-in my short experience, a low compression engine should kick over and fire easier than a high compression engine, so i wouldnt put so much focus on it. its gotta be a timing or firing order issue..if advancing the timing doesnt work id go with dicks suggestion that it might be firing on the wrong cylinders.

I have yet to attempt "creeping the timing." Ran out of daylight. I'll try this later in week
gootyman Avatar
Marc Gootman
Mesa, AZ, USA   usa
1977 MG MGB "Rusty"

Hey Mike, try and disconnect the Evap Controll system. You have spark and gas. I have been thinking and the only thing we really didn't look at the Evap Controll system. No air no start.
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