720World

Little Trucks, Big World

Hi y'all. This would be my first post here... please let me know if it's in the right place! 

I've got an '85 720 ST king cab 4x4 5spd. I've had it about 7 years, and I've done a lot of replacing over the years. Love the little truck, it goes anywhere (slowly)! 

I'm having an issue on cold start. In the morning, when I go to start the truck I have the following issues:

1. If I just get in and turn the key, it turns over fine, but won't catch. 

2. If I pump the pedal once, (to catch the high idle cam) it catches, fires a few times, then dies. 

3. If I pump the pedal exactly 12 times, turn the key, she fires, and idles great at 1K RPM. I usually let it idle there for a minute, then I blip the gas, and it knocks down to 600-700RPM, and runs ok-ish (under no load). As soon as I put a little gas on it though it starts to cough/ run rough... and you have to rev it a few times to get it moving. Before it warms up, it runs ok (but sputters a bit), and the idle can drop down to ~400 (rough) at stop lights – it won't die, but it coughs a bit. Once it's warm it runs jsut about perfectly – idling fine at 900rpm, and with no hesitation or coughing. 

The motor is a relatively fresh build (under 4k miles on the Z24rebuild), and I've got a webber on there. (All new vac lines, new coils, plugs and wires). I also replaced the in-pump fuel filter, and the crazy super secret fuel pump relay (although to be fair, just because I replaced it doens't mean it's fixed, ha). 

Any ideas on where to start? 

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How long have you had your Weber carb?My 85 engine look's similar to your's,have the NGK plug wires and and have my gas line looped like your's,on my Weber,I have a idle cut off solenoid,tried it without it and had the same problem as what your having.It controls my idle and helps it start right up.Some 720 drivers here will say you don't need it but I couldn't get mine right without it,it could be something else but my 720 runs awesome,had her since 93,24 years and got me Jasper remanufactured engine about 8 years ago,now have 55,000 miles on it,also their's a screw at the cam that you can adjust that will help you start it,on mine in the morning,I push the gas pedal to the floor and release,it starts up and idles to 2000 rpm's,then I tap gas pedal and it goes down to 850 rpm.What kind of fuel pump do you have?I have the Beck-Arnly oem type and a fram fuel filter,never had a issue with the fuel filter,am on my 3rd fuel pump,relay has been good,never a issue with it.I don't use a fuel pressure regulator,put a gauge on it before,just to see what it was reading and it was good.My spark plugs look good.I still use my vacuum lines,added one to the top of the T,V,V. port and ran it to the bottom of the filter plate,I have a you tube video,if you want to see.I also burn premium gas,2.55 a gallon here now, the cheap stuff is 1.91 .if I don't,the valves will rattle.https://www.youtube.com/watch?v=v5Fe9N0q2Kk&t=26s

Tommy,

Thanks for the detailed reply! I put the Webber on when the motor went in last fall (a few thousand miles on since then) and I've been trying to get 'er tuned right ever since. 

I'll try the idle cut off solenoid, sounds like if you were having the same issues that might be it! So that screws in under the air cleaner in front of the choke, and then you run power to it from the same cluster that powers the choke, correct?  Assuming it gets power only when the engine is on, just like the choke? (see attached pic > it replaces that screw correct?) 

As far as the fuel pump goes, I think it's original to the truck. I've never replaced it (Truck has ~219,000 miles, I only replaced the filter inside it once). I'll check out your video (thanks for sharing) about the added vac line from the T,V,V to the filter plate... sounds interesting. 

I also run premium and use the dello 400 – the combo of which seems to quiet the valves quite a bit.

Alex,if you get a idle cut off solenoid,here's a link to get one,stay away from Weber Direct parts,bought one from them and it's not right,Redline is the way to go.Just remove that screw that you have circled,be careful when you put it on it's a tight fit,if you have a dremel tool,grind it down to the left of the screw hole,on the piece that is sticking out,easy to strip out,trust me.http://www.ebay.com/itm/WEBER-Redline-32-36-DGV-DFV-Fuel-Shutoff-So...

Solid! Thanks for the link and the advice. Just ordered. 

Another thing Alex,the solenoid doesn't come with a rubber o- ring to seal it,don't use tephlon tape,Autozone has a pack of assortment o-rings on the shelve for about 3 bucks.

10-4 will do! 

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