Help! Truck's acting up!

[Justin]

Okay! So luckily I had a nice holiday (hope you did too) but, on my way back home my truck started acting up. 

 

I was driving about 60-65 mph and there was a quick, repetitive loss of power in a lurching fashion. The truck was acting like it was going to die but then would pick back up speed. I downshifted, only to find the same response in 4th gear, then eventually in 3rd also.

 

This continued the entire ride home, in just about every gear. Truck would "bog down" so bad all I could do was shift to neutral so it wouldn't die.

 

I had a similar experience in my re-wired 521 years ago when I used too small a main fuse, and the running lights couldn't be run at night because of too much of a power draw.

So, I tried killing my lights with no response.

 

 

My guess is either the cracked-head is cracking worse, the timing chain has stretched or maybe the transmission is going out? But I doubt it's the trans because the power loss occurred in every gear.

 

 

Please help!! I've got a new years party I want to be able to attend!! 

[Radiant-Designer]

I had something simmilar for a shirt bit a few days later my truck wouldn't start and it ended up being the fuel pump was done

 

May not be the same thing

[wayno]

Check your fuel filters, you have a weber, make sure to check that filter/screen also, it's in the big nut on the bottom in this photo.

[Justin]

Thanks man! It definitely could be a fuel problem! The guy I got it from said something about it acting up on bad gas, and then I cheaped out and got low octane today instead of the good stuff-

[ggzilla]

Inexpensive low-octane fuel is "good stuff". The more expensive high octane has no more cleaners and is not any better except it has higher octane. Even the least expensive fuel is required by government regulations to meet the same cleaning standards. That being said, you can get a bad batch of fuel with slight moisture in it. If that's what happened, time to clean the fuel bowl.

 

Also very likely is: ignition points & condensor. They are supposed to be changed every 12 months/12,000 miles.

 

Not likely: head gasket or timing chain problems.

[datzenmike]

....and certainly not the transmission.

[Justin]

Hey, this is why I'm here, so I won't have to ask stupid questions in the future!

 

It's an E.I. distributor, so the points aren't an issue.

 

Sounds like I'll be inspecting my fuel lines tomorrow!!

 

Thanks guys!!!

[jesusno2]

sounds about like what my 210 was doing my car completley died i still dunno what happened to this day im scared to drive it!

[ggzilla]

No Fear

[datzenmike]

Hey, this is why I'm here, so I won't have to ask stupid questions in the future! 

Just giving you a hard time. See wayno's answer.

Check your fuel filters, you have a weber, make sure to check that filter/screen also, it's in the big nut on the bottom in this photo.

Easy to change and cheap and very likely the cause. No harm done if it isn't and you can go on to taking the carb apart.

[wayno]

I actually don't know if he has a weber, I suppose I should have put a question mark on that particular question.

[Justin]

Well, I inspected my fuel lines and there was a murky brown collection at the base of the first fuel-filter before the fuel pump (there's a total of 3[!] fuel-screen's in this fuel line), and I'm hoping it was the reason for the poor fuel-flow. 

I had a new fuel filter lying around so I changed the old one out. Really hoping that was the issue.

 

Checked the filter on the carb (yes I have a weber) and the screen looked fine.

 

Haven't taken it for a test drive yet-

 

 

[ggzilla]

Now you are learning. Here's hoping.

[wayno]

Let's all cross are fingers.

[darrel]

take it for a test drive,,,, NOW!

[Justin]

Hahaha! Trust me, I want to! But the tank's on "E" and we might be waiting a day or two (or three or four): to fill it up!

[Justin]

Well it looks like I won't need to take it for a test drive because I just went to try and start it and the fuel pump does NOT appear to be drawing any fuel.

So now I need to decide where to wire in the electric fuel pump too, any suggestions?

[wayno]

Are you out of gas?

It's not going to pump anything if there is nothing in the tank to pump, you said it was on the "E" mark yesterday.

[Justin]

Ah-ha! Found out the problem was a massive fuel line clog BEFORE the filter. 

 

Gosh I love old cars!

[ggzilla]

Fuel line clog? Time to drain the fuel tank and rinse it out.

[datzenmike]

I'm afraid that might be the only way in the long run. Filters are easy to change on a 620 but constant random plugging is a pain.

 

Good news is the tank has a drain on the bottom. Dump it out when the level is low. Best to remove the tank and take the sensitive sender out. Put a few hand fulls of gravel in and shake it well. Dump out and rinse thoroughly with a garden hose and drain. Bring indoors overnight or use a hair drier. Install the sender. If you are careful and clean the O ring it is reusable. Remove the filter and blow compressed air through the lines to clear them. Try both directions.

 

Too bad the '73 does not have a return line. With a return line the fuel is constantly circulated and constantly filtered and any crap is caught in the filter and does not collect in the tank.

 

Assemble and be ready to change the filter because everything is stirred up. Your stock mechanical filter will likely be able to suck fuel through the now cleared lines.

 

Don't forget that you are working with highly flammable and if in an enclosed space... explosive gasoline. I used a brass punch to loosen the lock ring on the tank sender to avoid sparks. Be careful.

[wayno]

Sometimes the inside of the tank gets a lot of rust flakes floating around, while driving down the hiway these flakes get stuck on the end of the pick up tube in the tank and stop the fuel from flowing, when you shut off the engine, a little bit of fuel goes backwards and it can clear the tube, but when you start driving again the same thing happens.

Can you empty the tank, does it have a drain bolt?

In the past, what I did about this issue was pull the tank, empty it completely, I put a small piece of chain inside the tank and I shaked it around for a while till all the loose rust was removed, then I removed the chain and rinsed the tank out, I let it dry, then I put "Bill Hirsch" gas tank sealer inside the tank and rolled it around for a while till every inch had sealer on it, then I drained the extra back into the sealer container for the next tank, as this is what the can says to do, it worked great, and this tank was a pressurized tank that kept blowing holes in it when I used it, you could see holes, and it was like new after that treatment.

Don't get cheap on this, buy a good quality tank sealer, as you only want to do this once.

I have heard of others using round lead fish weights in the tank to remove the worst of the rust also, whatever knocks the flakes off is good.

I am not saying this is your issue, but it could be.

 

EDIT

I see this is a 620 now, as it is in the 620 section, so it likely has a drain bolt, empty the tank, and then firmly slap the bottom of the tank, can you hear rust rattling around in there?

[ggzilla]

> With a return line the fuel is constantly circulated and constantly filtered and any crap is caught in the filter and does not collect in the tank.

 

And any crud that is not caught in the filter goes right back into the tank.

 

In OP's case, the crud was BEFORE the main fuel filter, suggesting there might be a problem with the tank supply.

[datzenmike]

> With a return line the fuel is constantly circulated and constantly filtered and any crap is caught in the filter and does not collect in the tank.

 

And any crud that is not caught in the filter goes right back into the tank.

 

In OP's case, the crud was BEFORE the main fuel filter, suggesting there might be a problem with the tank supply.

Well, as all fuel has to go through the filter before either going to the carb or back to the tank I would say all crud is caught in the filter. Any 'crud' that gets past must be smaller than the filter can catch.

[ggzilla]

yes, and their is a lot of crud not caught by fuel filters. Especially if you use a Fram filter. I tried using one of those cheap glass inline micron filters but it was even less reliable.