Blue and White - exactly why I replaced cap, rotor, plugs and wires and then rebuilt and cleaned the carb. I was hoping for a smooth idle and consistent, easy starts. Air leaks are what's left on the list!

I went out tonight and reset the adjustment screws. First to 2.5 turns out then to 3. It will start up with just a pump or 2 on the gas pedal and then cranking, but it won't stay running without blipping the throttle. It's like it wants to idle... it's just not quite there. This is on the choke and it's chilly outside (around freezing right now).

Filthy Beast - I double checked the accelerator pump and I'm getting big fat squirts of gas so that seems to be working as designed.

I did notice after I pushed the pump some moisture (must be gas) appearing around the front left mounting stud. I know you're not supposed to really crank down on those nuts... the shop manual I have says 12-15 lbs and I'm already over that a little. Thoughts?

Have not tried slimming the choke down to 1/8 from 3/16.

It seems close. If I can get it to idle cold, I can check for leaks with carb cleaner or propane as suggested.

 

And the gas isnt coming from the fuel filter or power valve cover? If the power valve is not put in there pretty tight, it will leak out the hole in the cover.

Maybe the carb isnt fully seated in place. I had one that the studs were not straight and it needed a nudge to get it flat.

Sounds like you are heading in a direction though, so thumbs up.

 

Is the high idle setting on the cam correct? If you have to push the accelerator when its that cold out, but everything else seems fine and the choke is closed then it sounds like it isn't hitting the highest idle setting on the cam. I know you mentioned that its pointing to the "V" mark but I'd double check.

 

Also remember when adjusting the idle mixture, the engine will respond less the more the throttle butterflys are open. So if you have other issues, like a vacuum leak, and have twisted the idle speed screw in to keep it running, it may not respond at all to mixture adjustment.

 

A bit of success! And a bit left to figure out

First of all, thanks again to everyone helping out. This is a great forum even for complete novices like me.

I turned the fast idle screw in and that didn't help. I closed down the choke pull off clearance a bit and that got her to fire up straight away. This is with the idle mixture screws around 3 turns out. I didn't double check with a drill bit, but I'm guessing I'm closer to 1/8 rather than the 3/16 I was at.

Once it got running for a bit the RPMs started to climb up around 1500-1600, so I backed the fast idle screw back out and it's now idling on the choke around 1200-1250.

I let it keep warming up and blipped the throttle a little and it idled (the engine sounds... well, not smooth) around 800-900, however I think that was on the next to last fast idle cam because when I got into the cab and revved it with the gas pedal (I'm assuming now taking it completely off the choke) it won't idle at all without giving it fuel. I tried to turn in the curb idle screw a little but that didn't seem to help. Maybe it just needs a lot more? Maybe I need to know more!

So, starts and idles cold on the choke. Doesn't idle warm. But, progress!

While it's been running on the choke I've squirted carb cleaner all over the various vacuum lines and around the carb base and the brake booster hose and I don't notice any RPM change. Maybe some if I squirt it right at the backside of the EGR valve itself behind the carb... but I may be looking for something that's not there.

I also do not see gas seeping out around the base of the carb, so maybe that was just a flooded situation because of me manually mashing the throttle linkage while the engine was off?

I know it's probably not super helpful at this point, but I hooked the vacuum gauge up to the manifold port while idling on the choke and it reads 19 inches and the vacuum goes up to 25+ when the throttle is blipped and then right back to 19.

 

That's a step in the right direction as Jklnhyd said.... Have you let the engine warm up more (~120*F - 140*F on your temp gauge) before you hit the throttle? Sounds like she's still cold when you dis-engage the choke.

On most, if not all carbs, you can let the vehicle idle by itself after engaging the choke....blip the throttle on the easy side after a bit so the choke still stays engaged a skosh. Also, she'll start runnin "rich" with the choke closed too....good indication she's warmed up a bit.

Try giving the choke more time to do it's thing before you get in and put the pedal to the metal.....These vehicles aren't like the new ones.

Also - the EGR...next time you get her runnin'...try and squish the EGR diaphragm IN...like you're squeezing a tennis ball with two fingers.

What are the results?

 

Thanks Filthy Beast. I was just going by the temp gauge in the cab. The gauge has always run just under 1/2 when hot unless I'm stuck in traffic on the freeway and then it might get just beyond 1/2 way. I don't have a temp gauge. I could go get one of those point-and-shoot ones if I need to? Where would I point it?

I will try again and let it run for longer - or I could drive it around the block I guess.

I wish the fast idle cam wasn't so hard to see/get to behind the choke.

And... to now sound completely incompetent and risk having my truck keys taken away... I can't see any timing marks. My engine is super dirty... (fluid leaks are on the to do list), but I don't see anything. Is it hiding under the power steering pump bracket down by the fuel pump? Anyone have a photo of a 400/351m of where you'd point the timing light? I can also start a different thread for checking the timing...

 

Timing marks should be on pass. side of the timing cover, under/near alternator.

Also, if you're running ok or so-so with choke engaged, which means while running rich, then have issues once choke is taken off, I would still look for vacuum leaks, as this would indicate a lean condition without the choke on.

Really a properly setup carb, and ignition system shouldn't have much fits even in cold temps. I can get in my 78 w/ 351M w/ MC2150 and elec. choke when it's 20 outside and take off within seconds after starting the engine.

 

skyhawc is correct.

The timing pointer is on the passenger side of the engine and timing cover under the alternator.
The timing marks are on the harmonic dampner. Clean both well so you can see them.

Point your timing light down, about 45* from around the general vicinity of the battery area to the crank (balancer), being CAREFUL not to get tangled up in the alternator belt/pulley, etc.

If all this is still clear as horseshoe water, say something....I know someone will post up a picture ...or two.

 

This photo may help. Its my 400 after a timing set and balancer paint job.

 

Just curious if you did a compression test or if you have put a vacuum gauge on it. Forgive me if this was discussed, most of the responses are quite wordy and I skimmed.

 

"Dude"... that's crazy talk!

 

Sorry - not trying to be wordy, just trying to give the information I have so I'm not wasting all of your guys time who are trying to help me out!

Yes, I have put a vacuum gauge on it. No, I have not yet done a compression test. I'll try to do that today if it warms up a tiny bit.

Here's a less-than-stellar video of it at high idle yesterday

 

Ol School: I'll say it........Thanks for the picture....couldn't ask for a cleaner one.

 

Results of a dry and cold (it was snowing while I did this...) compression test