86 720 start up problems

[NST_311]

I recently got my 720 to start up again. It still however wants to stall right after I fire it up. It seems to be only on cold starts though. Do any of you guys have an idea what my problem is?

[Mr1der]

moved it over to the 720 forum so you can hopefully get fast and accurate help.

[PEZi]

so just on cold starts? once the truck warms does it run properly?

if so... with the stock carb these trucks are a bit finicky... you may need to check your fuel system for things like pump and filter... but for the most part you may just need a tune up with some new vac hoses and such

[NST_311]

Yes, just on cold starts. The funny thing is it used to do the same thing but vice versa. On cold starts it would start properly and on warm starts it wouldn't.

[PEZi]

yeah... when its cold, things like carb icing happen, fuel flow properties aren't what they should be... basically just make sure the fuel pump primes properly... and then make sure all the vac lines are good to go

mine used to have the same problem... it got better when i deleted the vac lines (don't know if that's an option for you or not) but what i used to do was keep my right foot on the gas at all time until it got warm... when coming to a stop i'd shift into neutral and left foot brake

now of course it runs fantastic on its own, but that's after a few years of work

[NST_311]

Alright then, I'll try it as soon as I get a chance. What strikes me as odd is it warms up fine. Also, why would it do it on warm starts too. I mean, it doesn't do that anymore, but still.

[NST_311]

Thanks for the advice. I wish I could say that's all this truck needed.

[flinterman2000]

Its definitely a fuel problem. If emissions are not a problem try deleting the vac lines except the one that goes to the dizzy. Also give the carb a good spray with a carb cleaner.

[Aven]

If your vac lines are original, start there and replace them, just as a matter of course. But if that doesn't make a difference, I'd start looking at the choke. Actually, I'd start with the choke relay first and then look at the choke.

[NST_311]

Hey guys, haven't been on in awhile. I've been so busy with graduation things haha. I finally got my truck to run pretty decently again. I still need to replace the vac lines, but that should be easy. All I ended up doing was putting in some new NGK Iridium spark plugs and they helped A BUNCH! I recently started having trouble with my radio. It seems something is not making contact in order for it to give me a signal correctly. It's probably just something with my screwed up electrics. I also have a weird rattling noise coming from under the truck. It gets really loud when I give it gas. I believe it's somewhere close to the exhaust or maybe even the transmission, but I'm not sure. Can you guys give me some advice??

[PEZi]

its probably a heat shield rattling

[fast720]

Hi
It could be like PEZi720 said a heat shield, or its pinging, is the sound like a ball bearing in a tin can ? do you get the noise if you sit parked and rev it up or only under load while driving ? Maybe your timing is way off ?

[NST_311]

It rattles under load and while its parked. Might be the heat shield actually. I know I have an exhaust leak, and I always thought maybe one of the exhaust hangers is lose but it might be the shield.

[PEZi]

yeah.. the reason i mention it is because mine had the same problem back when i got it...

the sound from under the truck is usually just the heat shield.... either the one by the cat or the one up front off of the header

[NST_311]

I think it might be the cat rattling on it's own. Something seems to be lose, maybe a hanger or something. And where exactly is the heat shield on the cat? Sorry I have to ask the obvious questions.

[PEZi]

its attached to the cat on the bottom.... its supposed to prevent fires if you park on high grass

[nlaforge13]

I recently got my 720 to start up again. It still however wants to stall right after I fire it up. It seems to be only on cold starts though. Do any of you guys have an idea what my problem is?

There is a valve in the intake that acts like a choke. There is a tube about 1inch diameter that runs down from this valve to the header. For the valve to open up it needs to be getting heat from the header. If you removed the muffler or added an after market exhaust it may take longer for the header to heat up, there for making this valve stay closed for longer.

[NST_311]

Hmmm.... It seems I don't have that heat shield haha. And, I was also informed by the truck's previous owner (my grandfather), that the exhaust hanger holding up the cat had broken before so he took the liberty of making one himself. He thinks it might have broken again sooo, maybe that will fix it.

[NST_311]

I recently got my 720 to start up again. It still however wants to stall right after I fire it up. It seems to be only on cold starts though. Do any of you guys have an idea what my problem is?

There is a valve in the intake that acts like a choke. There is a tube about 1inch diameter that runs down from this valve to the header. For the valve to open up it needs to be getting heat from the header. If you removed the muffler or added an after market exhaust it may take longer for the header to heat up, there for making this valve stay closed for longer.

Thanks for the advice I got it to work pretty good again so I'm ok haha. Also, I still have the stock exhaust, although it's basically rusted out.