Jump to content

lethargic Mechanical E7 350


masterwelder
 Share

Recommended Posts

My 96 RD roll off truck with a mechanical E7 350 and 8ll acts very lethargic or slow to rev up while driving or no load. It does make good boost while pulling at right around 30psi. If you mash the throttle no load, it dose skip as it revs up, but dose not do it while driving. It does pull fairly well though... but the water temp will go up quick while working. EGT never goes above 1000. It also seams to have a slight miss while idling. I have a e-7 300, E-6 300 and 350 and they seam so snappy when you crack the throttle, the E-7 350 sounds totally different like its nose is plugged.

I have had the valves adjusted, all new filters and muffler has been gutted other than that its stock. The motor was a remack rebuild in 2004. Tach is showing just a little over 20000 hours, 350k miles. No excessive smoke.

The truck is useable but this just isn't right. could it be slightly out of time? I think I covered the basics, any ideas?

I've driven like this since I bought it in the spring of this year and there has been no change.

Link to comment
Share on other sites

  • 3 weeks later...

Well I did not check the timing (still not sure how exactly to do it properly). But I did take the cover of that covers the screw that adjusts the puff limiter and screwed it all the way in, so I get as much fuel as I can. That made a difference on the bottom end. But what totally slipped my mind in my previous posts, and what now is more magnified by adding more fuel on the bottom is the slight miss I had while revving up. It also idles rough and really bad around 12 to 1400. So I'm now thinking injector? The miss is not noticeable while under load only when revving it up no load. I still have great boost and my EGT will never go above 8-900 no mater what.

Do I crack the injector line at the pump to try and identify a bad injector?

Link to comment
Share on other sites

Typically you crack the injector line at the injector end. Some things to try, sometimes you can "feel" the line and determine which injector might be missing. Another method it so put the end of a long screwdriver on the line near the injector, put your ear against the handle, and listen for the "thump". Or use a heat gun and check temps at the exhaust manifold for each cylinder. Good luck. BTW, I stayed at Holiday Inn a few months ago....does that count? :whistling:

Ken

HOF City, PRR Country, and Charter member of the "Mack Pack"

Link to comment
Share on other sites

You're injection pump might need a rebuild. My E7 started missing a little. I talked to my buddy and he said he had a E7 do that and it wasn't a dad miss, just a slight miss. Swapped pumps off a known good engine and it was fine. Mine has another issue, getting compression in the fuel return line! Wil fix that tomorrow...

If your puf limiter jigger wouldn't cause a miss. Be a sluggish turd, but wouldn't miss. Timing wouldn't make it miss either

Link to comment
Share on other sites

crack the injector line at what ever end is easiest to get to. you are looking for the one that causes the least amount of noticeable loss to the engine. as suggested a inferred heat gun will also work well. How long has it been since the valves have been adjusted? you could have a tight valve causing loss of compression or even a bad cam lobe not allowing a valve set to open, bent push rod etc. Are you making oil? or getting diluted oil? or does one exhaust port have a wet or dark color that doesn't match the others, if so this could be you problem cylinder.

Link to comment
Share on other sites

Sivart,

This reminds me of a problem that I had this last fall.

I have an 86 Pete 359 with a CAT 3406C mechanical motor. I have 30% over injectors from Pittsburg power. No extras on hand.

Suddenly we got a bit of a rough idle. Driver came home. Sounded OK then but from time to time we would hear that rough idle over the coming days. BUT IT GOT WORSE AN WORSE, over time! Still pulled good, but going from idle on up thru the gears it got worse and worse. Still at full throttle it seemed pretty good.

Finally as has been described above, we cracked the injector lines (at the pump) one at a time at idle and SURE ENOUGH we identified the culprit. BUT HOW TO GET THE 30% OVER REPLACEMENT???? Called Bruce Mallinson at Pittsburg Power and he made a RUSH ORDER to get it to me. Still took about 1 week. That engine just got SICKER AND SICKER as we kept using it cuz I needed to haul my apples and pears to market. They pyro never heated up though and we hauled load after load. But the BRAKE SAVER temp guage would climb erratically time to time.

Then the NEW 30% OVER injector came. I had the CAT SHOP put this in and adjust the valves and jake. WOW WHAT A DIFFERENCE!!!! We had kinda forgotten JUST HOW GOOD THAT MOTOR COULD RUN, when everything was RIGHT!!!!

I think that injector was a bit weak, even before it started to idle rough. BECAUSE it runs the best we have ever had it run now. I think it will out pull pretty much ANY MACK now!!!! LOL!!

GEOFF

P.S. Now I keep and extra injector on hand!

Link to comment
Share on other sites

204,

Well maybe except YOURS!!!

We try to AVOID your truck, take back roads and such. Anything to avoid getting into a head to head pull with your Mack. We think you load LIGHT or something!!!! LOL!!!!!! None of us can figure out just how that Mack of yours pulls SO GOOD!

I don't think you need ANY kind of tune up kit! GIVE US LOCAL FOLKS A CHANCE!!!

You might turn me into a Mack fan yet! After all I am over here on your forums. A good fruit market year, you might see some SUPERLINER in these parts hauling my apples and pears. Need to replenish the cash reserves first though!

GEOFF

  • Like 1
Link to comment
Share on other sites

PZ 1,

I thought about that. Cat guys didn't want to go into it twice. And we kept running her, thinking RIGHT AWAY I would get that new injector from P.Power. Old Pete, kept hauling the goods, running a bit sicker each day, and the 30% over injector was expected any day. Sure glad when it came though!

Even early on, when this injector was on going bad and it really only affected idle, we thought, none of my drivers could remember EXACTLY what kind of manifold pressure we HAD been getting when the truck was truly running well. This turned out to be 27 psi manifold pressure. When we were still hauling with this bad injector, I think we were getting 22 to 24 psi manifold pressure. We erroneously THOUGHT it was still running decent. Remember I have from 2 to 3 different drivers running this truck every week.

Sivart, you say you are getting 30 psi manifold pressure. That further confuses me, that is pretty doggone good I would say. Interesting side note, Bruce Mallinson at Pittsburg Power told me, if I remember correctly, with a 14.6L motor, or there abouts, to approximate horse power you take your manifold pressure in psi and multiply by 20. So in the case of my 3406 you would take 27psi times 20 equals 540 horsepower. I had this engine dyno'd and it came out to 537hp at the flywheel. Pretty doggone close to the Mallinson advice!

Keep us posted on what you find.

GEOFF

Link to comment
Share on other sites

I cracked the injectors an each one made the truck run rougher about the same amount. I did talk to my mechanic this week again about it and he is thinking it's in the pump and as long as I can live with it, to let it go. Earlier this past year he did adjust the valves and I'm not making oil. The motor was remack in 2004 but I don't necessarily think that would mean the injector pump was rebuilt also. The truck has 20000 hours showing. I would think that's pretty good time on the pump?

I guess it's a case of just how much I can live with. I don't like it- but its done it since I owned it. I'm more concerned that I'm not going to damage anything.

Turning the puff limiter screw in did help with the lethargic issue so that was positive. I guess it's time to look for a good pump shop or exchange. Exchange would be better do to down time.

Link to comment
Share on other sites

sivart does it hold rpm at what ever rpm you hold the throttle to? or does it lope, pulse, or flutter ?if it wont maintain a steady rpm I would suspect the pump of at least air getting into the system

She's steady at all RPM. I always thought at an idle it sounded more like an electric instead of a mechanical, if that makes any sense. Like I said though, it will miss as you rev it up no load

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...