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MG MGB Technical - Two problems....

Issue #1
Some posted answers on my last post....timing and backfire. Since we have back dated my friends car to a 25D distributor and his weber has been rebuilt. We are running much better but at the top of second gear and when under a load (up hill in 4th) the car wants to sputter some. You can put your foot into it and it will mostly clear up. On flat ground and cruising around town in 4th it runs great. Any ideas on the top end sputter?

Issue #2
None of the side lamps are burning. Do they go through a relay that would prevent them all from coming on? All other lights, signals, hazards are working now.


Thanks in advance!!

Bryan

Bryan,

You don't say what year the car is but if you go to www.advanceautowire.com you can find the circuits for your vehicle. Assuming it has 4 fuses you will see that all the lights you mention go through one of the top two fuses (red wires) both fuses are fed from the same red/green wire via a bridge on the back of the fuse block. If all the lights are out then the problem must be where the red/green meets the fuse block or earlier. If you have an earlier vehicle then these lights have no fuse which is common to all the lights (only the rears).

Overall the problem must be a bad connection but, if you have 4 fuses then start from there and work back. The fuse block is notorious for bad contacts.

John
John T

"If you have an earlier vehicle then these lights have no fuse "

Not quite. Immediately before the 4-fuse system (which uses each fuse to feed one side, front and rear) the parking lights were fused from in-line fuses, one for the front pair and one for the back pair. Other than that the principle is the same - either all bulbs or both fuses are blown, or the feed from the lighting switch to the two fuses is broken.

Or a combination of blown bulbs, a blown fuse, and various broken connections ...

On the splutter with non-standard ignition *and* carburation it could be anything. If the tach is steady then it isn't ignition LT, but could be HT, timing, or fuel. If it goes away with a heavier foot then it could be weak mixture, does pulling the choke a bit also cure it?
Paul Hunt 2

Issue #1
His car is a 77. No fuses in the fuse box are blown. I will print out the wiring diagram and see if we can find a broken end somewhere. I have checked the inline fuses and none of them are blown. There must be a bad lead somewhere. Sounds like we will be having fun tracing wires this weekend.



Issue # 2
This car has been off the road a while. We have put some water remover in the tank and topped it with good high octane fuel. At this point we have ran almost 20 gallons through it though. The tach is steady, it idles great. A heavy foot does help and the choke does also help. Sometimes the choke doenst completely clear it up though. I am leaning towards the mixture. To completely eliminate any ignition issues, we are replacing the points, condenser, rotor, and cap this weekend. After that, it would almost have to be in the mixture? The sputter only happens at the top of second gear and sometimes under load in 4th. The sputter last about 10 seconds usually.
Bryan

"I am leaning towards the mixture"

And a lean one at that :o)

For the lights first check for 12v on the front spades of the top two fuses with the main lighting switch in the first (or second) position(s). If there are no instrument lights either then the problem is almost certainly *at* the switch, either the switch itself or the red/green will be disconnected from it. If the instrument lighting is OK then there is a multi-way plug behind the dash that the red/green goes through - tricky to get at.

If you have 12v at the front of the fusebox check for it on the back spades. If it is there, then the problem lies out towards the lights, but as they are four separate circuits it would seem unlikely that all could be faulty but you can't discount it.

If at the front spades but not at the back spades then the problem lies in the fusebox, either with the fuses (connection between end-cap and fuse wire if the fusewire is *not* visibly burned out), or the end cap connections to the fuse holders, and finally there is a rivetted connection between the holders and the spades on the back of the fusebox, these can corrode. Testing on each spade, fuse holder and end-cap will tell you where the problem lies.
Paul Hunt 2

Bryan

IF you had water in the tank it could very well take more than a single application of water remover. Many many years ago I got a bad tank of gas in my VW van. fuel pump was delivering 10-20% water. Pumped out what we could and refilled using a water remover. It took many thousand miles and many applications of water remover to completely clear up the rough running.

FWIW

Larry
72BGT
Larry Hallanger

We are going to tune it some more this saturday then we have a road trip for sunday planned. I think more than anything it needs driven. If there is still some water in the tank hopefully we can burn a lot out. I too am now leaning towards the mixture..lean would make since, since it seems to starve on the top end and the choke does help.
Bryan

This thread was discussed between 25/09/2007 and 26/09/2007

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