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jdklan

E7 Engine Cranks But No Start

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I have a 2002 Mack RD688S with an E7 engine in it. When you turn the key on, it powers up and everything seems fine, but when you go to start it, it wont start. We changed the ECU with one that works, and we checked the VECU also

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Why are you asuming its an ecu problem? DO YOU have fuel preasure?

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I have a 2002 Mack RD688S with an E7 engine in it. When you turn the key on, it powers up and everything seems fine, but when you go to start it, it wont start. We changed the ECU with one that works, and we checked the VECU also

transfer pump if it has one. been there done that...............

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Is there any smoke coming out of the stack when you try to start it , if not it's not getting any fuel,if there is smoke it could be timeing. Let us know how you make out. Good Luck

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Is there any smoke coming out of the stack when you try to start it , if not it's not getting any fuel,if there is smoke it could be timeing. Let us know how you make out. Good Luck

You are thinking the timing may have slipped or what?

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I would make sure it's getting fuel before you do anything, it's not likley that the timing jumped but it is posible, it happend to me once when the keyway on the pump shaft broke. Is this a working truck or a running truck, did it just not start one day, if it fires up with a shot of eather than more than likley it's a fuel related problem. Crack a few inj lines on the pump and see if you have fuel when you turn it over.

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Did it just die suddenly on the road, or was it running OK when parked and then wouldn't start the next time you tried it?

If it just died suddenly on the road, check to see if the fuel pick up tube in the tank may have cracked or broken off.

About a month ago one of the IH semi tractors at work quit suddenly on the road, the fuel tank was 3/4 full, tried to get it going by filling the filter, but it would just run for a few seconds until the filter was empty again.

Anyhow, we put it on the lowboy trailer and hauled it back to the shop.

I hooked up a temporary fuel suction line and stuck the end of the line down into the fuel tank thru the filler neck, and the truck ran OK. This suggested that the pickup tube in the tank was defective.

Pulled the tank, and on the IH tank you can unscrew the pickup tube and remove it from the tank.

The pickup tube had fractured right at the very top and fallen into the tank, so even with a full fuel tank, it couldn't get fuel.

I made up a new pickup tube from a piece of electrical conduit and brazed it to the pipe fitting that attaches it to the tank, installed it and reinstalled the tank and all was well.

I know that most Mack tanks have the fuel pickup tube welded into the top of the tank, but if that turns out to be the problem, it's possible to use a hole saw and bore another hole in the top of the tank, weld in a female pipe fitting of the correct size and fabricate a screw in pickup tube as described earlier. That would be a lot better than buying a new $800.00 tank just because the pickup tube is bad.

Note - If you're not sure of the proper safety procedures for welding on a fuel tank, have it done by someone who is.

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First of all, I would like to thank everyone that has replied to this topic. All the information recieved has been very helpfull in diagnosing this.

I still havn't been able to get it to start, but I have more details on the situation.

The truck was driven into the shop and it just wouldn't start the next morning. We used starting fluid, and it wouldn't start. We checked the sensors and the ECU and the wiring harnesses and we still could'nt get it to start. Then, one morning for some reason I dont know, it started right up. We used the truck for about two days with no problems. Then the driver came in the next day to take it, and it wouln't start. It has been sitting for about a week, unable to start.

After reading the replies on this sight I cracked open a fuel injector line while some one else cranked the engine. Fuel was coming out of the line, and there was smoke coming out of the exhaughst.

I'm thinking its a timing problem, but maybe electrical since it had the problem before, but somehow fixed itself for a couple days. Any suggestions?

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Just a thought, what kind of fuel shut off does it have electric or cable, make sure it's opening all the way.I have a 90 mack that had an electric air shut off on the pump,I had to take it off and hook up a cable shut off because sometimes it wouldent shut the fuel off and sometimes it wouldent turn it on.

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So whats up,did you get her running ?

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We have had the same erratic problem with our quantum, a 1999 model with an EA7 470. Turns out the ECU is very sensitive to voltage drop. Anything below 11.5 volts and it gets the lack of will to work. Mack have installed a voltage warning light in the dash ( just a little red LED ). Is more of a problem on these buckets as the cab and chassis electrics are 24v and the engine is 12 volt. Check to see if you have a battery on the way out.

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94 Mack ch. 613. V max. 400. Just stopped have fuel come on the return line to tank did the filters  checked the little fuel solenoid works good. Cracked the injections lines. But no fuel there. Dealer sent me a square block with a solenoid on it  for 1200. Bucks. Haven't put it on yet.   Any help out there. 

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I had a truck where I had a similar problem... turns out it was a rock in the fuel tank and would only have the problem when it moved around and blocked the fuel intake from the tank. It would be a big issue for like a week and then for like 2 months it would be fine then act up again etc. But when it wasn't obstructing the intake she ran mint... until i found that out i was going absolutely batty.

 

Was an E7 also by the way. Thought it was electrical and fuel pump and all that hubub.

 

Hope that helps.

 

Sent from my SM-G892A using Tapatalk

 

 

 

 

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I have same problem with 1998 Mack e7 crank no start but no fuel too injector it has a  Electric  injector pump but on that not I found my starter has a really bad draw it’s pulling my 12.87 volts down to 8.6-9 volts  so I have a starter order for it so I’ll see how that works 

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We had an 05 e7 with a no start or had a rough idle  before the no start happened and we discovered the fuel line going over the motor went bad so we made all new fuel lines for them. It's hard to tell those coated lines go bad and they dry rotten and the cloth covering hides it. Then the fuel pump can't pull fuel as it's on the vacume side.

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