BRAT and the "Surging General Warning"

[newgen85brat]

I need more help. I have changed everything I can and my Brat is still surging around 1800 to 2800 rpm. I found another thread that was identical to my problem but it turned out to be a bared wire shorting out voltage to the disty. I had hope until that happened. Here is what the problem is: Some days the surging does not show up but then out of no where it will start. It is so bad that it will knock me down in rpm and damn near stop all motion. As soon as it drops slow enough to warrant shifting into 1st, the surging will stop and I can get over my problem. It will continue if I put slight load on the motor such as trying to maintain speed on an incline or anything while in 3rd and 4th. 2nd won't do it unless you are coming down from 3rd while trying to maintain some forward progress. It is not a cyclical surging so it is not something caused by rotation. It is more like a bucking and random. The car idles well although when it has just stopped surging, I can rev the engine to about 2k rpm and the idle will jump 250 rpm or so erratically. Also after these episodes the idle may be lower than usual. The thing that gets me is sometimes it runs fine then once it starts, it just gets worse until you use it the next time. It does not do it all the time, you cannot make it do it but once it does, it will do so for a while.

 

Here is the list of things I have tried: I put on a new fuel pump-no change. Changed all filters including a brand NOS fuel tank from SOA so it is not dirt or rust. I have put on a Weber Carb-NO change. I have put in a new coil-no change. I have new plug wires, rotor and disty cap-no change. I switched out my disty with one from a donor motor-no change. It has a new alternator and almost everything is new except the long block. The gas is good, it is not dieseling.

 

The only other things I am going to try is to look for a short in a wire to the distributor. I will pull the fuel cap next time to see if it is starvation. I put the Weber on and plugged everything-Could it be something I need to un plug? Oh, is there any type of ECU or "brain" that could be doing this?

 

I love my Brat and the only thing left to do is to rebuild a new block and swap them. It currently has a solid lifter 83 and I want to build the original 85 that has a broken crank. The motor runs fine but does have some piston slap although I think it would run for another 50k and still not have problems. I got a lot of money in this thing, there cannot be much left.......Thanks for the help guys.......

 

 

This was the final post in a problem that sounded identical to mine. Re: ea81 surging problem. HELP!!

 

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yes i did. Thought i posted it, but i guess i didnt. One day, i went through everything with a fine-tooth comb. Turns out that the part of wiring harness that runs across the bottom of the radiator was rubbing against the AC hardlines and exposed wires and they started shorting out and causing voltage drops. At one point, it was using the hardlines to complete the circuit somehow when i turned off the key, and would stay running even when i unhooked the battery and took it out.

[djellum]

the next dollar spent should be on test equipment.

 

the only thing replacing all that stuff does is create more variables and cost money. follow what the test equipment says and isolate the problem.

 

there is no ECU, so any wiring issues would likely be relays, actual shorts , or bad connections.

 

start with the basics, fuel and spark.

 

check timing with a light.

 

check with a fuel pressure gauge to see what pressure the weber is getting and if its consistent. what fuel pump did you replace it with? the fuel injected ones put out different pressure. Webers run weird if given out of spec fuel pressure.

 

check your lines, you may have blocked a return line or something when installing the webber. also check the tank vent tube and/or gas cap. also all the stock stuff should be completely removed when a weber is installed, may have created a vacuum leak.

 

hook up a vacuum gauge and see what it tells you. they can diagnose all kind of things like valve train problems and vacuum leaks.

 

compression test just in case, physically check for spark.

 

then when it acts up run the battery of tests again and see what changes. double check everything you have done, grounds on electrical, carb bolts tight, etc. EGR's, any of the leftover carb valves can all give you issues. test the components, don't replace them until you find one that is for sure broken.

[djellum]

the next dollar spent should be on test equipment.

 

the only thing replacing all that stuff does is create more variables and cost money. follow what the test equipment says and isolate the problem.

 

there is no ECU, so any wiring issues would likely be relays, actual shorts , or bad connections.

 

start with the basics, fuel and spark.

 

check timing with a light.

 

check with a fuel pressure gauge to see what pressure the weber is getting and if its consistent. what fuel pump did you replace it with? the fuel injected ones put out different pressure. Webers run weird if given out of spec fuel pressure.

 

check your lines, you may have blocked a return line or something when installing the webber. also check the tank vent tube and/or gas cap. also all the stock stuff should be completely removed when a weber is installed, may have created a vacuum leak.

 

hook up a vacuum gauge and see what it tells you. they can diagnose all kind of things like valve train problems and vacuum leaks.

 

compression test just in case, physically check for spark.

 

then when it acts up run the battery of tests again and see what changes. double check everything you have done, grounds on electrical, carb bolts tight, etc. EGR's, any of the leftover carb valves can all give you issues. test the components, don't replace them until you find one that is for sure broken.

[newgen85brat]

I will run some tests. I have already timed the engine, checked compression and the fuel pump was replaced with a factory replacement type that bolted into place just like OEM. Vacuum is good but I need to check it as it occurs and not occurring. I have seen that there are ECU boxes listed on ebay for 85 Brats so I guess that is an unknown variable. Thanks for the suggestions, I hope to find it and I will post it. The Brat had sat for years and many of the items I replaced have been for necessity anyway. The carb leaked, the fuel pump did not work, the fuel tank leaked, The plug wires were questionable, the tach was jumping and making strange clicking sound when you turned the engine off so it needed replacing. I don't feel bad for spending this money for 90% of this so that is not bad money spent. Since the thing was setting when I bought it, I knew there would be many items unknown and I would replace anyway. As far as fuel goes, I put a regulator inline at 3psi. I will keep trying, thanks again.

[newgen85brat]

Not that too many people are reading my posts but I found the problem. I put a fuel pressure guage on and found that I was only getting less than 1lb of pressure. I have no idea why but I then pinched the return line (the one from the fuel filter) and as a test put a clamp on it. The pressure went up to about 2lbs. I tried driving it and could not get it to surge at all. It ran great. Do you think the new fuel pump is weak or is that pressure normal? Thank you for your help. A few more minor problems and I think I will be done. I will start a new thread though.

[djellum]

how big is the fuel line? sounds like its too large and the pump cant keep up with the flow. If I remember right the weber likes around 3 psi, but you need to flow enough as well.

 

some people instal the regulator on the tank return instead of fuel line. sounds backwards, but supposedly it regulates the pressure that way, without altering the flow when the carb is asking for it. you can google it and see the arguments back and forth. That may be a problem, if you regulate the incoming fuel down, then it gets past the restriction and the carb and tank dont have enough resistance to keep up the psi.

 

test the pressure just after the pump just to make sure, as well as around your regulator. see if you can see any variance.

 

I would try moving the regulator to the downstream of the carb, see if it works better. if that doesnt do anything try the old pump that you took out and see if it changes.

 

many weber setups dont run return lines, you may look into running without one. just make sure you fully set it up for that. the fuel pump may or may not like the dead end system. personally I think the regulator might be the problem.