'76 Bus Bucking

[Velokid1]

Hey there howdy-

Colin helped me get my bus back on the road a few weeks ago. It's still needs a bit of tweaking but we had it running well. For about a week.

Right after I reached the bottom of the fuel tank (1/2 full for 2 years, then we filled it to about 3/4 full with fresh fuel) and filled up, she started bucking a little, then a lot.

It happens under load at mid-range RPMs. For instance, going up a grade and giving her a little gas. Also when going down a grade and over-running the engine then giving a *little* gas, she'll buck. (But not when going down a grade and giving more than a little gas.)

I added a bottle of FI cleaner, let it run for 20 minutes, then drove it and it ran great for a day, then started again.

At the moment, I am most suspicious of the fuel filter which was actually replaced when Colin was here but I'm thinking some junk from the bottom of the tank was stirred up when the tank was empty.

I welcome any input on these symptoms but my immediate question is this: I have 3 FLAPS within 100 yards of my work and I'd love to pick up a fuel filter today and switch it out.

Any of you know of a filter sold at the FLAPS that will suffice? I don't trust the clerks there with the same question.

Greg

[hambone]

It does sound fuel related. Check that filter, that's the easiest route. Barry had a very similar issue and had to replace the tank, rust clogging lines.

[Velokid1]

Thanks- do you know of a fuel filter sold at the FLAPS that will work?

I'm hoping/thinking it's not rust in the tank just because it's so arid here that things really don't rust easily. I had a buddy with a 68 VW truck with virtually no paint on it, just bare metal... had the tiniest bit of surface rust on it and that was it. Arid-zona.

[hambone]

What about fuel pressure? That is important.
I don't know about type4 filters.
Hey check electrial connections too. Just go stare at the engine, sometimes intuitively it'll tell ya.

[dtrumbo]

Thanks- do you know of a fuel filter sold at the FLAPS that will work?

http://www.napaonline.com/Search/Detail ... 74+2074027

If the link doesn't work, it's a NAPA Gold (made by Wix) FIL 3274. The Wix number is 33274 if your non-NAPA FLAPS sells Wix filters.

The filter is specific, so make sure you get the correct one. Just any ol' inline filter won't cut it.

[Randy in Maine]

While you are over at NAPA see if they have anything like this over there....

http://www.germansupply.com/home/custom ... at=&page=1

I have a couple of pair of needle nose vise grips that I put fuel line on the jaws that work well also.

[chitwnvw]

While you are over at NAPA see if they have anything like this over there....

http://www.germansupply.com/home/custom ... at=&page=1

I have a couple of pair of needle nose vise grips that I put fuel line on the jaws that work well also.

I second that. I bought these thinking I was being foolish with my money, but they make changing out a piece of fuel line a joy. Well maybe not a joy, but at worst my hands are gas stinky, and I don't have it running down my arms or squirting in my face...

It does sound like you are asking for more fuel and your system is unable to deliver it. Did your replaced filter show rust? You can also test your pump for volume pumped, IIRC ratwell has a procedure on how to do this.

[vdubzen]

wix filters are also available at autozone.

i use surgical clamps when working on my fuel lines. doesn't leave a mark on the fuel lines.

[Oregon72]

This will get er' done -

[hambone]

Ah yes the gentle taunts of a lunatic.

[Velokid1]

Thanks everybody. You all move faster than I do... I got the filter, but it's going to be a few days before I can even think of getting 30 minutes to crawl under and replace the fuel filter. Kids and all.

Step 1 will be to replace it and cut open the old one.

[Sluggo]

While you are over at NAPA see if they have anything like this over there....

http://www.germansupply.com/home/custom ... at=&page=1

I have a couple of pair of needle nose vise grips that I put fuel line on the jaws that work well also.

I bought a set of those at Pep Boys.

[Velokid1]

Hey folks. Thanks again for the help.

I replaced the fuel filter before the weekend and that seemed to fix the problem 100%... for about 1/2 the day. The fix was complete and immediate, started right up and didn't cough or sputter at all. That was 3 days ago and it's gotten progressively worse.

Now, that sounds to me like debris in the tank, but when I cut open the old fuel filter, I didn't see anything that *to me* led me to believe the fuel filter's flow was compromised at all. No dirtiness apparent, no specks visible to the naked eye.

So I guess next I'm going to run through and adjust the valves and reset the timing, then start from there.

One concern I have if you're reading this Colin is that I remember we did something funky with the AFM to compensate for something-or-other. "Six clicks counter-clockwise" sounds vaguely familiar.

[Randy in Maine]

Have you tested the Temp Sensor II with your handy volt ohm meter?

Just for grins when it is bucking, see what happens if you ground the harness wire (that the TSII plugs into) to see if that improves things?

[Velokid1]

Have you tested the Temp Sensor II with your handy volt ohm meter?

Just for grins when it is bucking, see what happens if you ground the harness wire (that the TSII plugs into) to see if that improves things?

I haven't but I guess I'll have to teach myself how.

I'm noticing that the symptom is starting to feel cold temps-dependent. Once the bus is up to operating temps, it runs fine.