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Discussion Starter #1
Hello, I am new to this forum and hoping to get some advice. I have been an auto tech for more then 30 years. I mainly worked for GM, so VW’s are a whole new world for me to work on. My daughter just got a 99” Beetle 2.0L 5speed. The car runs real bad cold and after it worms up it hesitates on acceleration. So far we have replaced the spark plugs, the coil pack, fuel filter, fuel pump and fuel pressure regulator. I have read a lot of post and most of all of you have the same issues. If I put a pair of vice-grips on the fuel return line just after the regulator, all my problem go away. Cold start, rough running and hesitation all disappear. Now I know that I can’t continue to run the car like this, even though I would like to, it’s not healthy for the plastic fuel rail. To give you a little history, we have had codes for misfires, injectors and O2 sensors. I have cleared the code and they haven’t returned, even with the engine running the way it is. I just cat put my finger on it. With the vice-grips on the return line, that little beetle runs like a scalded dog! So I know mechanically the engine and drive train are ok. I am going to clean the MAF sensor and the throttle body today and put an inline fuel pressure gauge to see the pressures as it runs down the road. Any suggestions or comments are welcome; I am at whit’s end with this little car!
 

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I think the inline fuel filter, so you can monitor the pressure is a great idea to monitor what is occuring under actual conditions. Seems to me that your restricting/blocking the return line would actually have the effect of increasing the fuel pressure, so low pressure could be the cause, even though you have replaced the fuel pump and fuel pressure regulator. Or is there a back-check in that line that could be failing, causing a loss of pressure? What made you attempt that solution (the vice-grips), by the way? Have you considered problems with the pick-up in the tank?

M.
 

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Discussion Starter #3
Blocking the return fuel line is an old throttle body injection trick I learned around 20 years ago when TBI first came out. The problem is, by blocking the return line will increase the fuel pressure, but is it compensating for a lean running engine (like a vacuum leak) I have been monkeying around with this car of months and still haven’t hit the nail on the head. I have checked this car out from top to bottom. I can’t find any vacuum leak, broken vacuum lines, clogged fuel pick up or lines. One interesting thing my daughter told me, she went to put about $15.00 in fuel in the tank and it took her al most 30 minutes to get the fuel in. that kind of leads me to a venting issue. I have looked, but haven’t found any thing yet. If you can’t put fuel in the tank, you can’t pump fuel out of the tank. Just like an old outboard engine with the tank vent close. I don’t know, still searching.
 

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I had the same fueling issue with a GM 6.0L. I have NEVER turned off a vehicle when fueling, and there are days, traveling, when I fill-up 4 and 5 times. In all climates and at all elevations, and NEVER had a problem. I leave the engine running to maintain the cruise setting and heat or a/c, and no need for anybody to go there, it is safe, no different than if the car on the other side of the pump is running.

I was dealing with a recent, recurring CEL that I hadn't taken care of. When fueling, IF the CEL was on, the vehicle would not take gas IF the engine was running. First time, I went pump to pump, then to another station thinking it was the friggin' fill nozzel on the pump. Figuring out it was the vehicle, and not the nozzle, I tried shutting off the engine, by the time I turned to the gas fill, NO PROBLEM! This repeated itself many times until I had the CEL iisue addressed.

Curious if your Daughter was fueling with or without the engine running when she experienced the problem.

I'm going to have to find the receipt and see what GM did to resolve the CEL, I know it was MAF and 02 sensor related. Since the resolve, I have no problem taking on fuel with the engine running. I'll find the receipt and post back.

M.
 

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Discussion Starter #5
Ok, here is an update. I haven’t put the fuel pressure gauge in yet. I just pulled and cleaned the MAF sensor. I pulled all the air intake ducts to clean and scrub the throttle body with cleaner and a tooth brush. The throttle body was nasty. I used the CRC throttle body cleaner and the CRC MAF sensor cleaner. Reinstalled everything and fired the beetle up. It didn’t want to run and stalled a couple of times. Got it running and took it out on the road. Bucking and misfiring until the check engine light came on. I returned to the house to hook up the scanner. Had a P0300, P0301, P0304 and P0102. I know the misfire codes, but the P0102 was a MAF low input. I cleared the codes and took her back out for a ride. All I can say is WOW, no more stumbling stalling or hesitation. All of my drivability problem are gone and it running like it had the vice grips on the return fuel line. I don’t know how it’s going to do on a cold start. We will just have to try it in the morning. And yes, I will write an update tomorrow. Ok as for the hard to fuel issue, I didn’t find anything yet. My daughter was filling it with everything turned off and I just put fuel in it the exact same way and had no trouble fueling it. As for “MyOtherRidesAVette” question, depending on the year and model of your GM 6.0L, some years have it written in the software in the power train computer to not allow you to fuel if the vehicle is on or running. It does this by closing off the vent and purge solenoids. No air out, no fuel in! I deal with this every day because I work for one of the biggest company in the word here in Orlando. (If you get what I mean. Mickey Mouse company) we have almost 4,000 GM vehicle that we take care of. From Cadillac’s to Top Kicks and also Hybrids as well. We are actually considered a GM repair and warranty facility. We have full access to GM’s support. Actually if you didn’t know GM also threw in a neat little feature, if you leave the fuel filler cap off, the vehicle will run like crap. Thanks a lot GM. I know we are getting off subject here, but if you have any GM question, I would be glad to answer them.
 

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It might have just been the pump at that station not making a good seal. My car seemed to do better at certain stations than others. Some, I could fuel up at full speed on the pump. Others, I could barely touch the handle to get it to fill up. It was a picky car, but I found which stations worked well locally and always filled up there if possible.
 
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