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Can't over 1500 RPMs

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Walk

Walk

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79 MGB w/ Webber Dgev: I was having a problem with the car skipping (missing) after driving it abut 35-40 miles. I put a new coil on it this morning, and drove it about 60 miles and it ran great. BUT, on my way back home I pulled away from a light and the car would not accelerate. I check my gauges and saw my oil pressure was OK (80), temp was normal, but the tack was only reading about 1500 rpms. I could nurse the car along and get it up to 40-45 MPH, until I would come to a big hill and then the speed would drop way off (RPMs stayed at 1200-1500). If I had to stop the car would idle ok, I have noticed that the muffler has gotten very loud and deep throated.

Just before this happened, I did hear something that sounded like a tinny or metal rattle from some place, I stopped and looked the car over (top and bottom) but didn't see any thing. Could a baffle come lose and is blocking the exhaust?
 
Walk said:
Could a baffle come lose and is blocking the exhaust?
Click to expand...
Very possible!
Another thing to check out is the fuel filter, make sure it is not partially clogged.
 
To me this sounds like fuel starvation. The next time the car refuses to go, try and be prepared with a clean bottle/jar. Disconnect the fuel supply hose at the carb and try and determine the fuel delivery rate while the car is acting up.

Out of curiosity, how long has it been since you changed fuel filters?
 
Check your timing. An engine will run rough if not adjusted properly and will cause different sounds to come from the exhaust pipe. Another issue could be that the fuel is getting too hot due to the fuel line being close to the manifold. This creates pockets in the gasoline.
 
Thanks guys, I have narrowed it down to the dizzy. I am only getting spark on plugs 1 & 2. I can pull 3&4 off and nothing happens, but if I pull 1 or 2 the engine dies.

I will pick up a new cap and rotor and see if that takes care of the problem.

I guess it wasn't designed to run well on two cylinders...

Pat
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]I can pull 3&4 off and nothing happens, but if I pull 1 or 2 the engine dies.[/QUOTE]

That exact problem was why I tossed the only Weber I've ever had on one of my personal cars....car ran fine with stock carbs but did exactly what you're describing with the Weber installed! No amount of work on the timing or distributor would straighten it out!
 
Thanks guys, I have narrowed it down to the dizzy. I am only getting spark on plugs 1 & 2. I can pull 3&4 off and nothing happens, but if I pull 1 or 2 the engine dies.

I will pick up a new cap and rotor and see if that takes care of the problem.

I guess it wasn't designed to run well on two cylinders...

Pat
 
The only exception [almost] to the "check for spark first" rule is if you have a DGV.

I still have a high G stumble I can't get rid of.

If we ever have a BCF fair....
I'll have the "throw the DGV through the tire" booth.
(6 throws for a buck & you win a Lucas flasher if you put it through) /bcforum/images/%%GRAEMLIN_URL%%/grin.gif
 
I've gotten pretty good at throwing them in the trash!
 
WTN is of course correct. I should have suggested that you confirm that you have working and set ignition before looking for problems with the fuel system.

However, I would not base the ignition tests strictly on the way the engine runs (or doesn't) when you pull off each spark plug. In addition to that test, put a test spark plug in the disconnected wire and rest the plug on a bare metal spot on the engine/chassis. Crank the engine while you look at the plug to see if you are getting spark on each wire. Also check the dizzy cap for cracking and burn marks on the chance that one plug is shorting out to another.

However, the fact that you can get it up to almost 40 mph while nursing it along and then have it loose power and slow down does sound more typical of fuel problems to me. BTW, when it looses power like this, does it feel like it's surging or is it steady and slow?
 
one point of interest that loosely relates to this situation because it has happened to me. If the heater valve starts leaking, you'll have misfires out the ying yang, if you can get the car started. However, it should be relatively easy to tell if your heater valve is leaking or not: water condensation on the inside of the dist cap, dampness on the outside, and possibly even a visible drip. Though, in my experience, I found that it is possible for the heater valve to not leak when the car is completely cool, and start leaking as the engine warms up.

However, as far as not getting over 1500RPMs goes, I've only had one experience with a similar situation. In my case, it was fuel starvation, due to an improperly rebuilt fuel pump.
 
Re: Can't over 1500 RPMs -Problem Sloved

Update;
I pulled the rotor and then the plastic case (ring) that holds the magnets. The end cap was loose and the magnets fell out or maybe some were out?? I put them back in and put the ring back on Now 1 & 3 are not firing and 2 & 4 are.

Magnets have a + and - to them, does anyone know if they have to go in a certain way in order to work right. IEA: all + sides facing in or all + sides facing out

Update:problem solved!!

It was a problem with the magnets! I think the top of the plastic ring came loose while I was diriving and one or magnets sliped out. When I put them all back in and tried it, a different set of plugs were dead. So I thought maybe they had to be all + side in or out. So I pulled it again and it took some time to figure out which was which, and then put them back in facing one direction (+ plus side facing out, I think) and put the ring back in and just took it for a great 6 mile dirve.

Thanks for all the help and advice you all sent me.

Pat
 
Re: Can't over 1500 RPMs -Problem Sloved

Another lil car hits the road again.
 
Re: Can't over 1500 RPMs -Problem Sloved

Good troubleshooting!
 
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