macksmoke

I'm really worried about increasing the RPM's with the auto trans. that's in it.

I need to find out what the RPM is. The cable is broke for the tach. I moved the plate forward when I took the spring out and the truck has alot more power at take off but not so much mid to full throttle. Where can I put a electronic RPM meter on this to get a accurite reading?

It sounds the smae as what I have. There is a plate under the puffer, is that the fuel plate? if I take the puffer out do I get more throttle?

I really don't think I have any shims in mine. I have a Bosch 95110112 pump. Can I turn this up a little?

I took the spring out of the puffer and it works great! Thanks so much for all your help! Does anyone know how to turn this up just a little bit? I have a automatic trans so I don't want to go to much! Thanks again! Steve.

Yes

I don't know what the boost is but it doesn't even try to build.

I might try taking the spring out.

On the back of the puffer there's a screw that I backed out, now it's even worse! If I put a longer screw in there to hold the puffer open do you think that'll work?

Why would it run worse when I disconnect the puffer?

The air and fuel filters were changed last fall, it didn't get better after that either. I'm going to start checking fuel lines for restrictions. Also I want to check the pump timing! I really need to fix this! It's my plow truck this year and most of my route is hills. This truck has a 10ft plow, 10ft wing and a 10 yrd sander.

Yesterday I disconnected the air from the puffer and plugged it, took it down the street and it was far worse the before!

I thought the puffer was different! Yes it has a air throttle and it is going wide open. This thing is bad we had a load of sand in it when we first got it and we back in some soft sand, we had to pull it out with the loader because it didn't have the power to climb out. When loaded it will not climb a hill out of 1st gear!

I get some smoke with the brakes applied also when I'm trying to go from a stop. It takes about 15 seconds for the boost to build enough to climb out of a hole. The air line that feeds the puff limiter comes from the intake manifold with nothing in between. There is also a fitting on the side at the front of the pump with a air line on one side and a fuel line on the other. I think it's the return line? I'm going to keep trying to get a picture on here!

Sorry guys! My pictures aren't showing up. The puff limiter on this is on the back about the throttle or govenor. I really cant find a small pecker anywhere! (I'm French!) I can't even find a relay valve on the intake. The air line to the puff limiter comes from the intake manifold direct. It seems like the vaceum from the manifold controls the puff limiter. Thanks again for all your help! Steve.

Is the puffer screw at the front or the back of the pump? Does it come out and do I have to plug the hole after?

Hey Macks, thats the same truck! I guess NYFD ordered 6 of theses as tankers, the at some point the put dumps on them to haul aspalt. I'll send some photos wen I get home today. How can I go about testing the puff limiter and relay? Thanks, Steve.

Are you loosing boost through a faulty air to air exchange, bad hose connection or bad hose?

I don't seem to have any air leaks, just low HP I think. Where in N.H. are you from? I'm in Wilton.

Sorry guys, its a old NYC truck. I'm not sure if its highway or sanitation or PW. It was a bright lime green when we got it and it had a plow on it. Anyways I dont see any turbo leaks and the turbine seems good. I don't seem to have any fuel restrictions, (return or feed). All cylinders are running about the same temperature. What I don't understand is why it takes so long for the boost to build, (15-30 seconds)? It's so bad that if I was loaded and came to a stop uphill, I may not be able to pull away! Sometimes I have to back up and get a running start.

Hi guys. I work for a small town and been here about a year. The truck I'm plowing with this year is a 1990 RD688SX. From what I hear is that there is only 8 of these made, its a old NYC fire truck. Now it has a 10 yard sander in the dump body with a 10 ft. plow on the front and a 10 ft. wing plow. The problem is that it has no power, from a stop up hill I wait about 20 seconds for the boost to build enough to move and sometimes thats not enough. I just did a valve adjustment and all filters are changed. I would like to turn this up but the place I was going to bring the pump to wants $1600-$1800 and I don't have much money to spend. Also I'm worried about the automatic Allison thats in it. Is there something that I'm missing? Or is this just a 270HP engine? Thanks for any feedback!!

1990 RD688SX

Engine:

E6-270

Serial# 0B095411GBA75936

Inj. pump:

Bosch#

95110112

Trans:

Allison model#

HT750-DR

Thanks, Steve.

Hi Guys, I have'nt been on since I got my new lower paying job.

I just heard today that Al Curtis of Global Truck Traders has passed. I know there are some on here that know him and I wanted to let you know. Rest in peace Al!!!!!!!

Thanks for the advice.

usually a coffee, cigarette, and a half hour does it

Wow! I was up at 4:30, had a coffee and a cigarette and at 5AM I was reading the NRA catalog. Good call!!!! You should be physic!!!

I just wonder when the Mack will start rejecting the Pete's parts and fall off, probably when going full speed down the driveway just before the fuel runs out.

mike

Yup, at 5 MPH with no windshield and when it's 20 degrees out!

I'll post you up too! Even though I think I saw a spot of dust on your garage floor!!!

The 7.3 is an animal. Transmissions where not there favorite. Drove one tow that had an auto and it ate that thing and the other had a 5 speed. It did good just thought it didn't have a low enough first. I think you'll be happy with that just put a fuel tank in the back as they like fuel but will drag anything you want anywhere. at 85 mph

You hit the nail on the head! The auto trans left stock would come apart. A rebuild with some updates will fix that. The best thing about the 7.3L is that it don't care if your empty or overloaded it will pull the same!

I had to explain it to my buddy, he has 7.3L and 6.0L. The 7.3L is a big block, the 6.0L is a small block. Kinda like 302 vs. 460 or 305 vs. 454 SEEEEEEEEE.?.?.