I can't win! Calling the big guns - please help - UPDATE

[K5_Fla]

1984 K5 Blazer 4x4 - Truck as a newer late 80’s TBI motor, converted to carb years ago. Basic 350, just has a edelbrock 1406 and intake.. nothing else from stock. Electric fuel pump in the tank.

The issue – truck recently started stalling out – like it running out of gas. Completely random at any speed...does NOT happen all the time. When the truck does this it will spit, sputter, RPM drop.. then cuts off. I have to pull over…crank it over a few times and continue on. Besides this issue – the truck runs real strong and no issues.

Things I have done - thinking I have a fuel delivery or possible ignition /spark issue I started working on it.

1. change the fuel filter – even though the filter that was already on the truck only had 1K miles on it. No help.

2. Rebuild the carb – wanted a reason to do this so I could install the edelbrock off road needles and seats. Rebuild everything on the carb and all adjustments are in spec, air / fuel mixture is correct. Truck does run stronger since carb rebuild.. but the random shut down issue is still there.

3. NEW OEM Fuel pump, sender, fuel tank , fresh fuel – no help

4. Changed ignition module and coil – no help

Thinking about changing the fuel pressure regulator – even though the one I have now is only around 6 months old…. And it’s a good one. What do you all think?


Side note – this truck is a project I have been working on for 2 years – so all the parts I replaced above only had about 2K miles on them to begin with. They already been replaced recently. I only drive the truck once a week to go to the store.

 

[nvrenuf]

Any chance of vapor lock?


Edit: *any* work performed prior to problem?

 

[K5_Fla]

I was thinking that too... but don't think this is vapro lock ... reason is that it happened yesterday morning only after the truck was running for 5 min. Nothing was really hot yet.. drove out of my driveway onto the street.... started to get into the gas and then bog...bog... stall.

 

[Big Ray]

what electric pump are you using?

If your using a tbi pump, you're getting waaaaay too much gas for a carb!!

Check the fuel pressure at the carb...

 

[K5_Fla]

I have a pressure regulator that is only 6 months old. Also have a new fuel pressure gauge… nice constant 5 psi.
Will be installing a brand new pressure regulator on Monday.. because I have changed every other damn thing.

 

[ktmoutfront]

When you restart it, what does it do. Start quick with no sputter? Long cranking with no gas? Long cranking with gas open? Etc..........

Watching the tail pipe when you restart it will tell you if it is too rich issue.

I had a 78 diesel I put a gas motor in. Non desired coil. Had the realtor on the fire wall. Truck would just die going down the road. Would always restart. Finally found the resistor wire was broke but worked most of the time.

Another thing to do the next time it happens is shut the truck off and check to see it the accelerator pump is squatting gas. Will tell you if the bowl is empty.

 

[badmix]

What part of Fla you in. Im in West Central (tampa) area. I dont much about edlebrook but have sorted my fair share out of my holley.

 

[nvrenuf]

Is the fuel pressure gauge inside or out? If inside, when it sputters and quits have you noticed if you are also losing pressure?

 

[kevin400ex]

check the magnetic pickup in your distributor. i had one give me intermitant issues such as yours and it drove me nuts chasing the problem down. only way i finally found it was i replaced the distributor. this after i had replaced the module, coil, cap rotor etc, the only thing i had not messed with was the pickup.

 

[Big Ray]

If you are using a HEI dizzy, MAKE SURE THE GROUND STRAP IS THERE!!!

ask me how I know....

 

[Confedneck]

I'm thinking a distributor issue.

 

[xpndbl3]

it's either losing fuel or spark, when it sputters and dies, spray starting fluid down the carb immediately, does it fire up or just crank and crank? How about yanking a wire and laying a spare spark plug on the wheel well? Does it spark or not? Those are your only choices, fuel or ignition

 

[Big Ray]

I had an 86 k5...I changed the ignition module and coil, forgot to install the ground strap in the cap under the coil...promptly fried both components again...

 

[badmix]

On my '84 I had to change the dizzy when I went from Quadrajet sorta kinda computer controlled to a Holley 570cfm truck avenger. Maybe it is something with the dizzy, esp. going from computer controlled FI to straight carb.

 

[K5_Fla]

The truck runs like a bat out of hell…. It’s perfect except for the random stumble/stall.

 

[Big Ray]

have the cap & rotor been changed recently...?

check wires for breaks / shorts...? (i pulled my hair out chasing a brake light problem..turned out the wire was broken right at the connector...)


did you put the dielectric grease on the new module when you installed it...? ( they tend to burn up if you don't)

I'm trying man, I'm trying...

 

[scooter122983]

if its cutting out randomly maybe the connections at the fuel pump are junk. Maybe it is cutting out when the wires get jarred like a bump or off camber situation. Wiggle them boys when the truck is running to see if it cuts off.

 

[K5_Fla]

good idea scotter.

Cap and rotor and wires are about 6 months old... and yes I used the greese today for the new module.

I have a new fuel pressure regulator coming monday. I really think it's fuel realted and not spark.

 

[xpndbl3]

so just ignoring what i posted and throwing parts at it rather than seeing if it is spark or fuel related....?

 

[K5_Fla]

bro... I can't spary starting fluid down the carb immediately when I'm running down the road at 45 mph. Your idea sounds good in therory.. but not possible. Very random issue and most the time it doesnt happen while at idel.

What I can do is temporary route my fuel pressure gauge on the hood so I can see while driving. This may be sometime I have to do so I know if I'm loosing pressure when the stalling comes