the dreaded relapse

Longbeach412 · Post by **Longbeach412** » Sat Mar 05, 2005 6:51 pm

well, I thought I was on a roll, tuned the motor and cured the miss, replaced the auto trannys modulator valve and cured the chuga-chug upon take off. So I decided to take the wife for a ride to display my wise investment and pick up the engine foam seal. On the way home she started bucking and would not take the gas, backfires and acts like a glogged fuel filter that won't let gas through. When you floor it and stay, it will buck and backfire but eventually will pick up PRMs and moves along till the next stop where it would barely idle. Limped home, changed the fuel filter and nothing changed. What is going on? anyone with such an experience? will go through the usual points, plugs check, but I just done that and she ran fine for a few days!!!!!!!

vwbill · Post by **vwbill** » Sat Mar 05, 2005 6:59 pm

Hey, check some of Ray's past post maybe under bucking. Did you do the timing with a Tach and a light? Is yours the 28degree(I think).
Did you check the MPS? I thought mine was ok but it really wasnt!
Make sure to check that copper braided wire on the point plate!! I was having a lot of trouble from mine which was broken and just attached under the point!!!!!! Bill

MGVWfan · Post by **MGVWfan** » Sat Mar 05, 2005 7:42 pm

Yeah, check to see if the MPS (if it's D-Jet) holds vacuum, then the usual ignition suspects as Bill noted. Sorry to hear of your woes, man.

Longbeach412 · Post by **Longbeach412** » Sun Mar 06, 2005 1:36 am

Yeah, once I get over the disgust, I will be checking all ign. & timing suspects. No, its a 74 L-jet. Yes I timed it with a light at 5 BTDC, 28 total advance. Thnx

raygreenwood · Post by **raygreenwood** » Sun Mar 06, 2005 5:59 am

Did you clean out the gas tank and remove that dang sock filter? It also sounds like it is fuel pressure related. Check for vacuum leaks.
This isalso common...like vwbill mentioned, when there is a short at the points plate in the dizzy...or a bad ground in the system....or ......most commonly...a rattly or poor connection at an injector or at the CHT. Ray

Longbeach412 · Post by **Longbeach412** » Sun Mar 06, 2005 7:56 am

No, I did not clean out the gas tank yet since I had earlier filled it up and wanted to wait till the gas was used up a bit. BUT now I am not so sure its a trouble source. When I removed the old filter, it was pure and clean as a whissle!, "sock filter".....time for a search on that

........ Will be re-checking all ign components, but it sure feels like fuel delivery to me. hmmm.....what's a CHT

?

MGVWfan · Post by **MGVWfan** » Sun Mar 06, 2005 10:56 am

Cylinder heat temp transducer. It's a thermistor in a bolt head that bolts up to the head. One wire coming out that's connected to the control unit.

The sock filter goes in the gas tank and is supposed to keep stuff out of the inlet pipe that feeds the fuel pump. Usually they just gum up and restrict flow after many years on the road. It comes out with the inlet and return pipes after you unscrew that big nut on the bottom of the tank (the one that's got the inlet and return pipes in the middle). Of course, the tank has to be empty when you do it...

Longbeach412 · Post by **Longbeach412** » Sun Mar 06, 2005 6:43 pm

Ok, the so called "temp sensor II", thanks for the enlightenment guys.

Longbeach412 · Post by **Longbeach412** » Mon Mar 07, 2005 11:24 am

Ok, update. Here's what I've done so far: Verified that, 1) coil ok, 2) dist. ok, 3) fuel pump relay ok, 4) head temp sensor solid & firm, 5) fuel tank ok when I replaced the filter I got a nice flow gasoline shower. Here is the symptom with a bit more observation: It starts ok and runs fine for 1-3 seconds then begins to heave, or fuel starve and dies. Next chance will check fuel pump flow & circuit, after that I am clueless

vwbill · Post by **vwbill** » Mon Mar 07, 2005 5:15 pm

Hey, you should pull that screw in the left fuel rail and put a clear hose on it(or fuel pressure gauge) and since she starts see if you get fuel all the way or do the Ray pump bypass setup!! Then you know its not a relay! Hey do you think you are just running off the cold start injector? Maybe Ray or someone knows how that switch over is made? I guess you could pull it or didnt Ray say that the ground lead goes through there??? Sorry not more help! bill

ubercrap · Post by **ubercrap** » Mon Mar 07, 2005 5:36 pm

vwbill wrote:Hey, you should pull that screw in the left fuel rail and put a clear hose on it(or fuel pressure gauge) and since she starts see if you get fuel all the way or do the Ray pump bypass setup!! Then you know its not a relay! Hey do you think you are just running off the cold start injector? Maybe Ray or someone knows how that switch over is made? I guess you could pull it or didnt Ray say that the ground lead goes through there??? Sorry not more help! bill

Could very well be running off of fuel from the cold start injector for a few seconds, at least that's what CIS will do if the pressure isn't correct, although I know this system is drastically different.

vwbill · Post by **vwbill** » Mon Mar 07, 2005 6:51 pm

Stupid question, so if not the fuel pressure or fuel problem could the aux air regulator do this by creating a vacuum leak?? Bill

Longbeach412 · Post by **Longbeach412** » Mon Mar 07, 2005 7:57 pm

I did do a premitive testing to verify that gas is getting pumped all the way to the injectors. I manually actuated he AFM flap with ign. on and fuel line to cols start valve disconnected and gas gushed out alright. One thing I noticed however that the flap was not really close to being fully closed, it took a bit of travel to close it. Isn't that thing supposed to be at or near the closed position?

vwbill · Post by **vwbill** » Tue Mar 08, 2005 4:58 pm

Hey guys, could he be getting gas at the cold start valve but the return line or pressure reg stop it from flowing beyond that? It seems weird that she starts then proceeds to miss and stalls like something is opening up after she gets warmer? Can he bypass the fuel system by running a pump like Ray said directly from a good source to the fuel Ray or is it just better to check the pressure at the fuel rail screw? If she starts and a vacuum issue is the problem can he bypass the aux air reg by closing off that line to see if that is a issue? bill
P.s. i loved my L-jet on my old 412 only had a point arm break and she drove great and had good Mpg(28-32) and MPH!

raygreenwood · Post by **raygreenwood** » Tue Mar 08, 2005 5:17 pm

If the flap is not closing properly, it may not be opening properly. That maybe affecting the fuel pump switch. It will definately keep you from getting the proper fuel mixture. Dis you check the resistance on that CHT sensor? Ray

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the dreaded relapse

the dreaded relapse

Sorry you having the trouble!!!

Dang! Man!

Re: Dang! Man!

aux air regulator?

You're gonna find this problem!!