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Engine running like crap


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Hey all. I have a 1974 1.8 Liter in my 69 521. It has been running great. One day on the way home from work it acted like the ignition key got turned off. As it rolled to a stop it started up again but ran very very bad. I replaced all the following. Points, plugs, wires, rotor, Dist cap, coil and wiring from battery to resistor and coil. It started up and ran awesome for about 3-4 minutes and then started the same crap. The plugs are dry black and sooty. The fuel pump pumps like hell and when I pump the accelerator, I have a good shot of gas into the carb. I again replaced the plugs and points today trying to get it back home from a test drive and it ran ok for about 30 seconds then started the same shit. The weber carb is brand new about 3-4 months ago but I dont want to spend $350.00 for a new carb to find that aint it. It has started back firing while its running if you gas it too much. It runs OK at idle but give it the least but of gas and ir runs real bad and back fires occasionally. Anyone have any ideas? I am starting to think maybe valves or timing chain??????????


Any help appreciated



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The plugs are dry black and sooty

This is a sign your running rich. when it died how much fuel did you have? and how dirty was your fuel filter?


It sounds like you have some soot built up in the carb. pull the needles clean them and clean the ports out also with carb clean.


after that tune the hell out of it.



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The plugs are dry black and sooty.


This would indicate carb way too rich likely flooding.


The weber carb is brand new about 3-4 months ago


Brand new, or just new for this car? Either way Webers are sensitive to too much fuel pressure. New they aren't so bad but older ones are worse. Usually 3 PSI or just under is fine.


Is the choke on or stuck on?

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Yes, it is either:

- Spark


- Fuel


For spark, make sure the dwell is correct and a big fat yellow (not blue) spark

For Fuel, clean the carb air jets. If they are partially blocked, the air/fuel ratio is way too rich.


My Datsun carb has done this 3 times in the last 2 years. Not black-plug rich, but stops running, won't barely idle, etc. All three times it was crud in the main jets, even after putting new fuel filter in.

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Fuel filter very clean, choke completely open. EI plate broke so I am back to points and condenser which have been changed, sprayed the hell out of the carb with carb cleaner and it didn't make any difference. It seems to idle OK but as soon as you put any gas to it at all it runs so bad you can barely go 2-3 MPH. The weber carb was brand spankin new. The strange thing is in the past the problem has been somewhat intermittent. One day it ran so bad on the way to work I barely made it and when I got off it ran fine??? I guess I will take the carb apart and look and see as well as check the fuel pump pressure. Thanks for the input-



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sounds like its flooding out to me too, had this happen to couple of hitatchis and a weber ive had in the past too. float stuck open on em and flooded em out. But on the other hand with the motorcycle carbs i used for a little bit the o rings i used got smashed causing a vacuum leak and it ran like carp too. make sure you dont have any big vacuum leaks.

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Took the top of the carb and blew all the jets and holes out including the float pin. Checked all the valve lash, put additional ground strap on. Getting good spark from coil wire to ground although its kinda thin not really "Fat" as has been described here in a post. Dont really know what to look for here so I am kinda SOL as far as is the spark good enough or not. Wiped off the plugs started it up and it ran great for almost 30 seconds. Got around the block and barely made it home. Checked for vacuum leaks and didnt find anything. When I pulled the plugs this time, 1 and 3 were black and dry and 2 and 4 were black and wet.........The idle mixture screw is 1 1/2 turns out. Man this is getting to be no fun at all.........................

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Sunk float? Too high float level? Too much fuel pressure like Datzenmike said? Either way it sounds like its running rich to the point of sounding like its "gurgling"?


I had this problem while working the kinks out of my 720 after I redid the headgasket. For some reason, due to gunk in the needle/seat or something, I had a too much gas in the bowl problem. After it sat for awhile, it was fine at first, but 30 seconds later it was running like crap. Luckily, whatever caused my float chamber to fill with gas resolved on its own. I DO have a stock Hitachi, but the principle is the same.


From what I've read, a Weber seems easy to check the float level, and float problems can cause what you are describing.

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Ok got a fuel presure gauge and it shows 4 psi. Is this too much? If so would it damage anything in the carb needing repair? Got an in-line spark tester and it shows strong spark to all plugs. Bead blasted the plugs ad started it up without the fuel line connected to the carb and it still is all garbled up. BTW is the ballast resistor supposed to get real hot to the touch? Starting to think maybe a carb change is required what do you guys suggest?

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Ballast will get hot!


Webers like 3 or under. More than that can over power the float and force fuel into the bowl, overfilling it.


Is your Weber jetted for an L16? If over jetted it will run rich. What jets are in it... maybe someone with one can say if they are too big.

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Coil was changed as was ballast resistorguess I will investigate that after work today. As for the jets, it has run fine with this carb for months so doubt that it would be the jets. I really appreciate all the help guys. I'll get it figured out here shortly I am sure.

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Stock coil is about 1.6 and ballast about 1.6 ohms


Not all ballallast resisitors are the same ohms. They look the same but some can be very low.


Your carb is fine I bet its the coil set up. its cooking the coil and or ballsast which is arching the points.

I bet if you ck the points it pitted out already inside

Edited by banzai510(hainz)
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Well I decided to start all over again with all the new information in my head and this is what I found. I only have 10.9 volts to the ballast resistor. Maybe the ignition switch or fuse block anyway I am going to rewire that circuit first. Next I have only 4.3 volts from the resistor to the coil. From what Ihave read I gather that the resistor is supposed to reduce you incoming 12 volts down to about 9 volts to save on point wear. I am going to get a correct resistor/coil combination that is made to work together. At first I had bypassed the ignition switch and hot wired the circuit. Since it didnt fix it immediately I ended up removing that wiring. I think I am on the right track and would like to thank you all for your advice.

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"I only have 10.9 volts "

then you only have 10.9 at the fuse and fusable link


yes fix THIS first. So ck the battery cables and clean the post

then clean the fuse ends/posts


This recently happen to my 521

Had 12volt at battery post but started looseing voltage on the cable clamp post. so it was corrossion between the post and cable.


then look at the coil ,ballast resisitor set up

Edited by banzai510(hainz)
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Low voltage and the stock coil won't fire correctly. I am a bit surprised, as my EDIS crank trigger system works flawlessy at 11 volts.


Yes, fix that voltage drop. Your Ballast Resistor may be OK, check the ohms first before deciding to replace it.

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Well spent some time with the old meter today. Got 12.6 volts at battery and at fuse box connections. only 10 volts on wire to coil which comes from ignition switch I believe. Bad ignition switch?? I hooked a solid 12.6 to the resistor and got 6 volts at the coil, isnt this low? I thought 9 volts at the coil was about right. Thoughts..............

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Good idea to check the ignition switch. I dont really know what voltage I should have at the coil. All the Google info I have read talks about 12 volts to the coil at Start position and then the juice runs through the resistor in the run position. What I have found stated the resistor drops the voltage to about 9 volts. If 6 is good then I am ok if it nees to be 9 looks like I have the wrong ballast resistor maybe?????????

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Pull the Blk/wht wire off the ballast and see if the BLK/WHT wire has 12 volts or hopefully what ever th battery is reading. With the Key "ON" .. If that reads OK then switch would be ok

If you get 10volts then switch is added alot of resisitance. Find connection and clean maybe trouble shoot from there. Wiggle it, WD40 it .


Put the stock coil and resisitor back in. I know you didnt throw it away!!!!!!!


id you have 12v coil

and a coil of 1.6 ohms and a ballast of 1.6 ohms the ballast would drop 6 volts and the coil would drop 6 volts giving a totoal of 12volts. This is a basic ohms law formula without going into great detail but as a car runs the voltage might really be higher like 14volts so assume it can be a little higher running at the coil above 6 volts 6-9 should be just fine.



always reck the point gap and condensor ect.....

Edited by banzai510(hainz)
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Pretty much figured out its not in the ignition. Ignition switch was causing resistance so I wired 12.6 volts direct to the resistor to eliminate that possibility, bead blasted the plugs and cant even get it to keep running at idle now. Took the weber apart and cleaned everything out. Didnt find any problems at all, float level good etc. SOOOOOOOOO In the am I am going to replace the plugs with high $ good ones and see what I have, if still the same I guess I will have to listen to my wife. She says this all started after the three days of heavy rain we had and maybe I have water in the gas? So I will pump some gas out and see what she looks like and gravity feed some fresh gas in just to keep her quiet. My god I will never live it downif she is right. Maybe I should just scrap the truck before testing the gas LOL. BTW I am a retired cop and I never arrested anyone for violating OHMs law....LOL


Do I simply measure across the coil or resistor with an ohm meter and should get whatever the ohms are?? I use the meter for continuity testing but have never measured any resistance with it as havenever had the need until now.


Thanks to everyone



Edited by Drfixit
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