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Carburation problem...

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Andre the Giant

Jedi Hopeful
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Yesterday when leaving work for lunch, my '79 MG Midget idled just fine. When I gave it gas though, the car would pretty much just die. There was no sputtering, no backfires, the RPM would just drop until the engine died. I gave it full choke and it seemed to do a little bit better, but still pretty pathetic. I limped it towards home so I could swap vehicles, then all of the sudden, the engine starts running fine. I'm thinking that there wasn't enough fuel reaching the carb.

So here are my theories:

1) Fuel filter/line clogged
2) Water or other foreign substance in fuel system
3) Clogged jet assembly
4) Fuel pump bad

Please feel free to list any other ideas.

Thanks

[ 05-02-2003: Message edited by: Andre the Giant ]</p>
 
clogged vapor return line? - results in vacuum created in fuel tank - fuel starvation even though everything else is working - just happened to me recently

loose or cracked vacuum line?

bad vacuum advance on dist.?

good luck
 
Here's what I've done so far. I put in a fresh tank of gas with "heat" (supposed to remove water from gas) I adjusted the timing, adjusted the mixture, gave the fuel pump a whack with a screwdriver, cleaned the screen in the fuel pump.

The problem persists. When I'm driving, especially up hill, its like the carb is starved of gasoline. I have no power, and eventually I will come to a stop if I don't choke the carb. But when I take my foot off the gas, the car idles fine.

My car is dessmogged. Here are a few questions.

1) I replaced my '79 ZS carb with one from a '75 or '76. The replacement carb doesn't have a pipe for the vaccumm advance for the distributor. What do I do about the vaccumm advance?

2) stupid question really, but where the heck is the fuel filter located? I'd like to replace it.

I'm thinking of checking the float chamber to see if the jet or valve is clogged. I'll keep you updated.
 
I believe that there is a 'screen' on the pump! That being said, what is your float level set at?? First thing I would do is just open the fuel line and see how much is coming thru!! It only takes a couple of psi!! If that checks out, o to float settings!! If that fails it may be your condensor!!!!
 
there is no fuel filter unless someone installed one after it was purchased. look between the fuel pump and the carb. if theres none there, consider investing in one.
 
My '76 had an inline fuel filter, in the line going into the carb (obviously!). Victoria British sold it as a replacement part, and IIRC, my trusty Bentley manual gave instructions on replacing the fuel filter (I should dig the book out and check on that, tho). Just follow the fuel intake hose away from the carb, and if there's a filter, you'll find it (plasticky thing that's clear on my old car).
-William
 
And now, the continuing saga of Andy's MG.

I don't think the problem is fuel delivery. I disconnected the fuel line to the carb and cranked the engine, in just 10 cranks of the engine, it squirted out a couple ounces of fuel.

I removed the carb, cleaned the float bowl, jet and set the float level. All seem to be fine. I even swapped the autostart/choke assembly with another carb that I have and the problem perisists.

My latest theory is that the intake manifold bolts are loose, or air is getting sucked into the plugged up port where the EGR valve used to be. When at idle, there may not be enough vacuum to suck air though the leaky gasket or plug, but when accelerating, it might gulp some air. That might lean up the mixture enough to cause problems... am I right?
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I'll update you on Tuesday.
 
I found a few problems with the intake manifold and am currently replacing it with the one that came with the mid-70's ZS carb that I am using. (The 79 manifold has too many ports to plug up, and I'm afraid that some of them were leaking.)

The front manifold stud/bolt may be stripped. I haven't taken a super close look at it to see if it's the nut or stud.

When I get all this done, if the problem persists, I'm wondering if there's a breakdown in the ignition system. The distributor cap and rotor look good, so do the wires, but I guess that's not a very good indication is it?

Edit: another update. The stud/bolt are fine. I am currently giving the carb one more cleaning before hooking everything back up. I had a thought and decided to ask a very basic question here... Some have suggested that I check the points on the distributor. Does the '79 distributor have points and a condensor? I didn't think it did.

[ 05-14-2003: Message edited by: Andre the Giant ]</p>
 
I think your problem is in ignition, not in fuel delivery. Give your MG a major electrical tune up by replacing spark plugs, wire set, distributor cap and rotor. If your 79 has an Opus distributor (solid state) get rid of it immediately and replace it with a Pektronic conversion. Do not use the original Opus distributor if you have one, get an older points type distributor and use it for the Pektronic conversion. Also check any electrical connections servicing the ignition system. I think your problem will be solved with the above. If you follow up with me, tell me what type of distributor your have in your 79 and I might have more advice to offer. Best regards,
 
By the way Andre, If you are a giant, how do you drive a Midget?
 
I just found out again that a bad condensor can make for some weird problems!! Condensors are cheap and easy!! So, if it was me, I would try that first!!
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well, after a beer!!
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[ 05-14-2003: Message edited by: Gary Lloyd ]</p>
 
I'm not really a giant, (6'1", 240), I'm not really a wrestling fan, and my name is really Andrew not Andre. But I liked the wrestler's appearance in "The Princess' Bride" so that's the name I've been using. Everyone I know is amazed that I can fit in the Midget, but I find it quite comfy.

I didn't get to tinker today, but I will on Friday evening and saturday. I don't really know what OPUS is, but I know my distributor/ignition system matches that of a CEI system for a '79 non-california emissions Midget. It has the Lucas
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amplifier underneath the coil. I will try to gather more information on Friday after I put the carb side of the engine back together.
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I'll be sure to drink a few homebrews while busting my knuckles.

Thanks for the advice, I'll have more questions soon.

Andre...I mean, Andrew.

Edit: I took a look at Moss motors' diagram for the OPUS distributor and I do not have that model. Mine is a CEI. Is that as bad? Worse? Also, where does one find this Pektronics conversion kit of which you speak? Will it work on a CEI distributor or should I find a different Dist. model?

Enquiring minds want to know

Thanks again.

[ 05-15-2003: Message edited by: Andre the Giant ]</p>
 
Andrew, I am 6'2' and about 200. I cannot fit in a midget or sprite so I take my hat off to you. You must have very flexible joints. If you have a seperate amplifier under the coil, then you have a CEI. It is a very good system and I prefer it to the Pektronic. If it has problems it is in the amplifier (a black box about 3x4x1). It can be easily rebuilt since it has a GM module as the major element. The CEI distributor is not adaptable to the Pektronic. Geographically, where are you? I might be able to help you out. A weak coil could also cause your problem. Does your coil show any oil leakage or other degradation? Best regards.
 
I'm in what is affectionately known as "Swampeast Missouri." Cape Girardeau is about 100 miles from the Arkansas border and right along the Mississippi river. Is there any information on the web about how to rebuild the amplifier? The coil appears to be intact (no oil leakage), it does however look old, dirty, and could be ready for replacement. I guess I'll be placing an order with Victoria British or Moss Motors!
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Thanks

Andy

[ 05-16-2003: Message edited by: Andre the Giant ]</p>
 
After reassembling the carb side of the engine, I tore into the electrical side. I pulled all the plugs and cleaned them. (they are only 4 months old) I checked the rotor, dist cap, plug wires, coil and external amplifier. I found some sort of bug web/coccoon in the external amp and cleaned it outa there. I reassembled the electrical system and lo and behold, the car runs quite nicely.

In spite of that fact, I placed an order today for a new rotor, dist. cap, coil, and plug wire set. It's not that expensive, its easy to replace those components, and I want to have this car running tip top for the endurance rally in St Louis!!!
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It probaly wasn't carburation!! See you in St Looooooie!!
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Look for the guy that is gonna win the award for coming the furthest in a MG!!!
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Gary, somebody will be there from Alaska. There will be no uglier cars than mine though
 
and Andre, I've heard some stories about that rally from Phil. 100 miles in reverse?
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