Hesitates at full throttle

79930 · 05-31-2004, 09:43 AM

I have a 79 930 (23000 miles) with a hestitation problem at full throttle. I drove it last week and she ran fine. Filled her up with gas, drove about 4 miles and she started missing under full throttle. I thought for sure I had a batch of bad gas. I drained the tank and pulled out the plug on the bottom of the tank and checked the filter and it was clean. I then filled her back up with fresh gas and had the same problem.

I then turned my focus to the ignition system. I changed the distr. cap, rotor, plugs and wires, took her out for a spin - no luck same problems.

It revs up fine, does not hesitate or miss, but when I drive her and give her the gas she stumbles and hestitates from 3000 rpm and up. (She will run fine all the way to 6700 rpms if I go easy on her)

Could I have a bad coil - will they fail under load? Or could my fuel filter in the engine compartment be dirty? I figured if the filter in the tank is clean it would be safe to think my filter in the engine compartment would be ok.

I did notice when I replaced the distr cap and rotor that the contacts were black and the wire from the distr. to the coil was very black along with the distr cap connection at the coil wire.

Fuel problem or coil problem or injectors?

Any thoughts would be appreicated.

Thanks
Kevin

tmk · tmk's Garage

I had the same thing with my 78SC. I went through all the same things coil, plugs, Cap rotor Etc. It was the fuel pump. Installed a new one and all is good.

79930 · 05-31-2004, 12:33 PM

Thanks for the advise. Did you change the coil? By the looks of the contacts I am leaning towards the coil. It's a little cheaper than the fuel pump. I don't want to spend 240.00 for a new pump only to find it's the coil. I have ordered the coil from our host. If that doesn't work I try the pump. I'm sure the coil and pump have not been replaced since the car was built.

Thanks again, I'll keep you posted on what I find.

Kevin

79930 · 05-31-2004, 04:58 PM

Please advise how to bleed the fuel system. I understand that the fuel system has to be bled after installing a fuel filter or fuel pump.

Thanks
Kevin

dean · 05-31-2004, 06:01 PM

Before you replace stuff you should find out if it is bad. I would buy sone CIS gauges and a factory manual and test the fuel system. You can check your pressures and your fuel pump output. Your problem does sound like ign. though.

dean · 05-31-2004, 06:03 PM

Oh yea, to bleed the system. Key on, air filter housing removed, push down on the air flapper until the injectors squeal.

79930 · 06-08-2004, 02:28 PM

I have changed the plugs, rotor, distr., distr. cap, wires, fuel filter (in tank and external) and the front fuel pump. Still no luck. I have the rear fuel pump ordered and should arrive tomorrow. Hope this fixes the problem or will be bumming.

Thanks for all your help.

Kevin
_________

01 - Chevy Duramax
99 - MB TurboDiesel
85 - CJ-7 (Rock Crawler)
79 - 930
54 - MGTD

79930 · 06-09-2004, 04:57 PM

Somebody please help!!! I have now replaced the rear fuel pump and I am still having the same problem. Please someone give me some ideas. I am running out of patience and money. Could it be an injector?

HELP!!!!

Kevin

kqw · 06-09-2004, 05:05 PM

Not sure on CIS....

But...do you have a "full Throttle Sensor"

Also, I have seen 3 threads here regarding the same type of issue.

They all happened after a recent fill up. THere's some BS gas going around.

Jesset100 · Jesset100's Garage

79930 I used to work with this guy that had a 79 jeep. Well when he hammered on it the jeep would take off for about 3 to 4 seconds then start to sputter. Come to find out it was a rubber fuel line that would collapse as the fuel pump sucking fuel out of the tank.

79930 · 06-10-2004, 07:26 AM

Wayne, Please help. I checked the filter on the WUR and it was dirty. Cleaned it and reinstalled and it runs a little better. Could it be the WUR

Please Help

Kevin

RazorRacer · 06-10-2004, 01:26 PM

Does it have to do with full throttle or high rpm? It could be that your timing is not set right. Just loosen the 13 mm nut next to the distributor cap, mark where it was set, turn it clockwise a few degrees and try again. Also you might want to clean out the inside of the distributor cap with some carb cleaner.