Inherited a 77 M880 ... sandy color, registered as NGOUNG

[autonovice]

Looking for tune-up specs or how tos

Does anyone has the tune-up spec/emission sticker under the hood for the M880?
I am looking for the factory spec and/or how to tune-up tips ....
timing - TDC? or 10 BTDC?
idle rpm - 700 rpm?
how to adjust distributor vacuum advance
how to adjust 2bbl carb fuel mixture

I am having issues w/ performance ... the beast hesitates and/or stalls at acceleration, can't idle in drive at stop signs. I set the timing to be 10BTDC
and idle at 700rpm but not to sure how to adjust carb fuel mixture so i opened
half turn more.

thanks in advance

 

[N1265]

I do not have a sticker under the hood, But I think there is a "data plate " .

According to the " organizational maintenance " lesson plan ( pg 120 ) , the timing is set to 3deg BTDC, the RPM's are set at 750 and the carb adjustment is done with an engine analyzer through the exhaust.


but I got mine set at 8 deg. BTDC to help it start in the winter .....


Also , remember to plug the vaccume advance when you set your timing, otherwise it won't be set at the right value.


the vaccume advance is done with weights in the distribitor and I am not aware if they are adjustable, but if the rpm rise when you connect the hose it is working. if not, check to see if the diafram on the advance is bad.

 

[autonovice]

Thanx N1265 ... I will try to retune my engine again.

 

[N1265]

StiffyLS
11-13-2005, 03:39 AM

Hi, what are the factory settings for the Carter BBD's mixture screws?

Thanks

MagicRat
11-13-2005, 09:41 AM

You mean the idle mixture screws?
Usually the base line setting is to turn the screws in all the way and then back them out one and a half turns.

At that point you ca turn them a bit to fine tune them. One way to do so is to warm up the engine, and plug in a vacuum gauge to a manifold vacuum source (this is a souce that sucks most at idle)

You should show about 18-22 mmHg of vacuum at idle. Then turn the mixture screws in or your a bit until you reach the highest possible vacuum reading at a normal idle speed.

 

[N1265]

also, I told you wrong in my previous post, if you plug the vacuum line back in ( where it goes on the passenger side port ) it might not raise the RPM at idle, but you can check to see if the advance is working by applying vacuum to the hose with an alternative source .

If you don't have a vacuum pump try plugging it in where the choke goes or get a longer hose and suck on it.

 

[autonovice]

Thanks N1265 ... my truck doesnt stall anymore when I accelerate! But I got another bug ...
It wont idle well (and stall) in D; only in P or N!! I opened up the idle mixture screws
(by one turn) and checked for vacuum leaks (OK). It still doesnt improve. Help! Carb rebuild?
Idle in P is now at 1200RPM and it idled ok in P at 700RPM.

 

[N1265]

1200 rpm is way to high, the idle screws only effect the idle, at 1200 rpm you are bypassing the idle adjustments all together...

if you are sure you do not have a vacume leak try this,

with the engine warm...

1) set both idle screws ( the two in front of the carb ) 1 1/2 to 2 1/2 turns out. ( I suspect you are already close to this now ) make sure both are set the same.

2) after setting the idle screws, turn the idle adjustment screw ( the big one by the throttle cable ) out till the truck drops down to 750 rpm.

3) plug the vaccume advance and make sure the timing is between
3 deg BTDC and 8 deg BTDC.

4) If you have to re-adjust the timing, then re-check the RPM and adjust if nessary by using the Idle adjustment screw next to the throttle cable ( as in step two ) and re-attach the vacume to the vacume advance.

Test drive and tell us the results....

 

[autonovice]

Ok ... The beast finally idles in D now .. but rough still.
What I had to do is back out the idle mixture screws 5.5 turns!!
Is this normal? I tried 6 and 7 turns no different from here.

Idle mixture is adjusted by turn out the screws until
the engine is happy in P and then in D. I started with
2.5 turns as suggested and kept turning out. I will need
to invest in a vacuum meter to do fine adjustment.

Timing is OK at 4BTDC using the scale on the engine timing cover
and vacuum advance disconnected and plugged.

Vacuum leak checked OK, with RPM check while engine is running.
I disconected & plugged all vacuum hoses: brake booster,
3 lines from carb feeding out.

I noted gunk in my fuel filter, replaced and used compressed
air to blow the fuel line back to fuel tank hoping to clear any
residue back to tank. I don't know how to test my fuel pump
but noted barely visible fuel trickled in from the clear filter
while the engine was running. There were fuel feeding the carb
if I loosen fuel inlet from carb side.

I checked with NAPA but unsure which carb rebuild
kit to buy. Where do I find the carb part number?
It is a Carter 2bbl.

My conclusion is there is not enough fuel coming in
may due to carb clogging or fuel pump too weak. May be
this why I had to turn my idle mixture screws out so far.
Any suggestion? rebuild carb?, new fuel pump? drop and cleany my fuel
tank?

One last thing ... as I was revving the engine to test .... I noted the crank
pulley goes in and out ... may be by .5 inch. Should this be normal?
I thought it shouldnt do this at all. I will need to check the crank
pulley bolt. What is the spec torque for this?

 

[Bob H]

IDLE MIXTURES @ 5.5 TURNS!
Carb likely has blockages in it.
clear in line fuel filters rarely fill up for some reason
Carter BBD, rebuild kits show up on ebay often.
Any decent parts guy can get the rebuild kit.

Crank pully moving in and out!!!!!!!!!! problem there.

77 Dodge factory service manuals are availible from dodgeboysnet@hotmail.com

 

[N1265]

5.5 turn on these screws is not normal, with gunk in the fuel filter bob is right in thinking that the carb ( and probable the entire fuel system needs cleaned ) maybe this truck was vandalised with the "sugar in the gas tank trick " at some point in its life and may be your problem. Also, there is a screen at the end of the pickup tube in the tank, and usually if you blow out the gas line with air it will blow the screen off the end of the tube ( which is no big deal ) and should eliminate it from being a problem. However if you suspect a fuel flow problem hook the inlet tube for the fuel pump to a 1 gal. can, this will help you rule out a problem with the tank , lines or pickup screen...

A good vaccume gage can also be used as a pressure gage, and this you can use to test your fuel pump. It should be putting out around 6 lbs. of pressure. test it before the fuel filter, don't let a trickle of gas going to the carb worry you. the carb will only take what it needs and when it is ideling it don't need much.

The crankshaft moving in and out is called " crankshaft end play " it indicates a high millage motor with a warn thrust bearing, usually no big deal ( in a small amount ) but I have never seen one with the amount you are describing
( 1/2 in. ) something is up there, are you sure the crank itself is moving, or is the pulley just bent and makes it look like it is moving ? The best way to check this is ( with the engine off ) crawl under the truck with a crow bar, put it in
between the block and pulley and gently pry the crank towards the front of the truck and take a measurement between the back side of the pulley and block. Then reach up with two hands on the front side of the pulley and push it back towards the rear of the truck until it wont move back any further and take another measurement between the pulley and block. this way you will have a more accurate figure for the crankshaft end play. If it really has this amount of end play the front main and rear main oil seal should be leaking, and if it is leaking does the truck have enough oil in it to pump up the lifters ? Just a thought...

I am not sure of the correct torque for the pulley bolt but 75 ft lbs should be enough. the big thing is just to make sure the pulley is seated onto the face of the crankshaft ( no play between the pulley and shaft ) you will figure this out while under there and pushing on the pulley by hand.


let us know how you make out ....


.

 

[autonovice]

I finally had time to work on this truck ...

The fuel pump is pushing 7lbs while the engine is cranking so I think my pump is still good.
I had the fuel tank out, looked inside thru the filler inlet. Looks ok. I dont see much
gunk inside. I need to open the sending unit and the filler neck to have a closer examination.
This will be a bitch as I the screws are all rusted and ceased

I am thinking of replacing the fuel sending unit while I have it out. Should I do it?
The old one still works. Or just replace the gaskets and put it back. Found a NOS from Mopar Truck Parts - NOS and Used Dodge Truck Parts - Dodge Truck Parts ... near home so cheaper on shipping.
Please let me know if there are other sources?

Thanks for all the help so far ... this site is great.

 

[N1265]

There is not a lot that can go wrong with the sending unit, if it is working I would leave it alone,

my truck still has the orginal sending unit , ( but I did replace the float )