Hard start /No start

[gearhead204]

can you put air to the fuel tank when the truck is cold? I often put a regulated air supply (5-8)psi. to trouble shoot these issues. if any thing starts to (sweat) fuel, it can also let in air! being a temp sensitive issue I would suspect a crack in a fitting or hard O-rings or seals in the fuel system, also your fuel lines are now over 20 years old you could have a brittle or failing inner hose liner allowing air into the system. You can also make a test hose from clear tubing and install between the fuel filter and the suction side of the hand priming pump. then run the truck and watch for air bubbles traveling through the tube, then shut down and see if you see a back flow in the hose. also have you checked the tank vents? if they are plugged you may have a vacuum causing you problems.

[mrsmackpaul]

ok I drew this a while ago should explain it fairly well so excuse my chicken scratch but it should be clear enough

The important thing to understand is that the fuel siphons back thru the to the tank when the motor is not running which it is meant to do but and this is were most people dont understand is that the return is just as important as the supply side I had to have it explained to me in great detail before the penny dropped but it really is as simple as I have explained before and the tell tale signs to look for are

does it make smoke as soon as the motor winds over if so it has fuel

if there is no smoke it has no fuel because it has siphoned out and air has gone in on the return side of it

if it has smoke and wont start it is a compression problem

Paul

[Monk31]

I would check your transfer pump I think and check your fuel lines

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[theakerstwo]

There is some useless information on this post.

[Jamkar]

I've had a similar type problem with my '95 vmac, runs good all day, shut down for the night and then just winds over the next morn. Turned out to be an under dash electrical issue. Big solenoid was a bit lazy, give it a bit of a 'tap' and she'd fire right up. Good luck mate.

[bbigrig]

Rough idle/both black/white smoke on start up:

Your truck being a 96 it should be V-mac II and were well known to over fuel for the first few seconds (like white smoke and cough like an SOB on start up in cold weather) it's the "programming" and seemed to be a big issue with 95-97 engines on cold start.We had 3 trucks with that cold start up issue.

These start issues with V-Mac II seem only present in cold climate operations. should be less apparent if truck is warm or plugged in over night.

For the no start issue:

Your rack actuator controls fuel delivery out of the pump.the actuator is what turns your rack to no fuel on key off cycles and moves the rack on all inputs from your throttle position sensor when the key is on.(Actuator must be energized to allow any fuel delivery to the injectors) if it fails it will not allow fuel to be injected.(no fuel rack position) If it is starting to fail you can have hard start issues that seem like lack of prime issues but its not. actuator issues do not usually show lack of power issues, usually issues on start up.

I had had 97 that basically did the same thing. Off and on issues that seemed like loss of prime for months. Finally truck wouldn't start no matter how much cranking. Actuator failed.

Check for codes in ECM. You mave have rack actuator fail codes. A loose injector harness plug or loose pins (grey plug that attaches to pump) can cause this issue as well. Twist the plug during start up and see if it makes me difference for what seems to be a lack of prime or no start only.

This is all if your fuel system is otherwise as it should be, not sucking air or leaking.

[theakerstwo]

The main reason a VMAC starts up with some blue smoke and misses for a few seconds is because when no oil pressure the econovance goes into retard timing mode.When you start it it builds oil pressure and goes to a advance mode for white smoke control.The timing is jerked around as the ecm sees need but will retard to some degree at full load.As the engine wears and also as the seals in the econovance wears it takes longer running after a start up to clear the exhaust.

[bbigrig]

New econvance and remaned engine had the same issues. The complaints were not blue smoke, it was white , chugging till it all evened out.(incomplete combustion from over fuel cold)

Seemed the programing didn't adjust the rack as fast with V-mac II. V-mac I didn't have this issue on the same set up pump/econovance. It was originally a common complaint from first time owners up here on cold start days who bought VMAC II trucks. Nature of the beast and one of the better engines.

[theakerstwo]

Retard timing means white or unburnt fuel till the econvance gets the timing advanced.Yes they were the best or last of the best engines mack made.Same way with a STC cummins.Peec cat same way.They lay in a retarded position when dead and advance when started.That the reason they miss for a few seconds on start up.

[R.E.D]

Since it rained today I dropped by the yard to see if any leaks in the fuel lines were present. Before cranking I pumped the hand prime pump like ten times until it got real stiff. Then I cranked it for about 8 seconds and it started.it ran rough for first 3 seconds with white smoke and then it ran normal.

[R.E.D]

As gearhead204 said the lines are old .I will start there then tackling the wet spots on the fuel lines.i have no blink codes except the 1-7 because of a bad coolant sensor connector.

[gearhead204]

does this truck have a KYSOR system installed on it ? if so there might be a issue with it or it could be part of the issue. the kysor system typically consists of a fuel shut off solenoid, and oil pressure sw. and a temp sw. most have an override button you depress while cranking the engine to bypass the low oil pressure sw.

[mrsmackpaul]

Since it rained today I dropped by the yard to see if any leaks in the fuel lines were present. Before cranking I pumped the hand prime pump like ten times until it got real stiff. Then I cranked it for about 8 seconds and it started.it ran rough for first 3 seconds with white smoke and then it ran normal.

If you had to hand pump the primer and it changed as in the effort required and then it started fine it would lead me to think that you are loosing prime when the trucks not running

but I could and most likely wrong as I always say what would I know LOL

Paul

[bbigrig]

Never seen a V-mac equipped engine with the Kysor system. One should make a other redundant. It was stated earlier that the engine is V-mac. Stating that you have found the hand primer soft narrows this down to a mechanical fuel system failure.

[R.E.D]

How would I know if I have a kysor system.the only override button I have is the one for the engine shutdown override. The hand primer was soft, but not that soft like when fresh filters are installed and one has to pump for ever to get it to be stiff.

[thomastractorsvc]

I agree with Paul and Glens comments on losing prime. If you pumped it up and it started that means you are losing fuel back to the tank. I would check the lift or transfer pump first and fix the leaks as allowing air in the system only makes it worse.

Had an R had the same problem if it sat for more than a day, unfortunately for me I did not have primer until I changed out the transfer pump and was a PIA to get started. It had a seal that was bad and allowed air in the system and allowed the fuel to siphon back to the tank on the inlet side and would pull the fuel out of the filters back to the tank.

You could add two cheap shut offs and see which side is bleeding back and figure out from where. I would almost bet it is at the lift/transfer pump that is allowing it to drain back.

[R.E.D]

The lift and transfer pump are they the same thing?I'm guessing it's the one that the hand primer screws into.the shutoff valve I'm assume will go before the pump?

[theakerstwo]

Same thing its just way people look at it.

[mrsmackpaul]

the lift pump is meant to allow it to siphon back when not running thats why the air is coming in the return line if you pull a lift pump apart they arent a real tight fit even when new

if you fix all the tiny leaks you will fined a huge improvement for little money spent

Paul

[theakerstwo]

That is not true.For years we have know that the valves in the lift pump leaks down the fuel and you no start.

[terry]

What Glenn said!

[mrsmackpaul]

what ever !!!!!

Im not gunna have a bun fight it really doesnt matter at all you can change the lift pump and it may fix it but the end of the day air is getting in the fuel system some how and it is the return side fix the little fuel leaks the truck will start fine for ever and a day or change the lift it will start fine maybe but it doesnt really matter you still gunna have a fuel leak thats gunna cause problems now or in the future

yes there is some useless and thats fine I wont add anymore after all Im just a farmer what would I know SFA

good luck RED

[R.E.D]

I thank everyone for their replies and input.

This whole week is been in the low 50s .Everytime I get to the yard I have been pumping the hand primer and the old dog has been starting.i have been looking at a lift pump online made by PAI.I would like to know what you guys think of that brand when it comes to mack.Are they a quality replacement part provider for our trucks?i have bought some items in the past made by them in the local truck parts store (Mack dealer is 40 miles from me at Mcarty) and the salesmen say they are great , but I know they say what they need to say in order to sell.

[theakerstwo]

RED are you talking about the hand primer that you want to replace or the transfere that bolts to the side of the injection pump?The hand primer can leak down also but so can the fuel pump bolted to the side of the injection pump.PAI is good parts.

[R.E.D]

I was referring to the lift/transfer pump.the hand primer I replaced about 3 months ago since (57 bucks at mack) it was leaking when pushed and truck was dying on the middle of the freeway due to air in the lines.