98 e7 427 fuel issues

[mjrays]

I have a 98 e7 427 I'm having fuel issues I replaced lift pump all lines look good truck runs fine plenty of power then out of no where starts running like crap some times comes out of it or sometimes stalls will start back up after cranking for a bit any help would be greatly appreciated 

[fjh]

So there is alot of posts on this subject on the site do a search! check the cheap and easy stuff it can be many things as simple as the fuel tank vent plugged to bad fuel lines! Start tring stuff and eliminating things!

[JoeH]

Is this a fully mechanical fuel pump, or vmac II or vmac III fuel system? A picture of the right side of the engine would give the guys on here an idea of what exactly you're driving so they can tailor their responses.

Have you changed your fuel filters? Did you get bad fuel from a transfer tank or gas station? When you change your fuel filters dump the fuel in the old filters into a mason jar so you can see if you're sucking water. The water and fuel will stratify, meaning the water will be on the bottom and the fuel on top. You'll see a clear line between them.

I think some engine setups run a pressure relief valve on the return side of the fuel in order to keep fuel pressure up.  You could have a failing relief valve? 

You could also have the Dreaded Piece of Trash floating around in your fuel tank, blocking the suction line. Some idiots try to seal a leaking fuel cap with a plastic bag (super dumb) and sometimes people unknowingly let the foil seal from a bottle of fuel treatment go into the tank. Either one can cause you this headache.

[mjrays]

11 hours ago, mjrays said:

I have a 98 e7 427 I'm having fuel issues I replaced lift pump all lines look good truck runs fine plenty of power then out of no where starts running like crap some times comes out of it or sometimes stalls will start back up after cranking for a bit any help would be greatly appreciated 

 

[dexter860]

V Mac 3 .

[dexter860]

Maybe Ecm or electrical related?

[Joey Mack]

I doubt ECM...  Check the condition of the fuse box under the center of the windshield. Fuse 40 is the ECM.  Looks like you have an RD 688S... Also, when it's running, unplug the cam sensor, if it shuts off the flywheel sensor or wires are bad,  if it stays running, plug it back in and unplug the flywheel sensor. If it shuts off, the cam sensor is bad... 2 simple steps that are FREE to do. If you would like, you can go to flywheel sensor wires and peel back the loom to see if the wires are damaged.. I have seen that a lot.  Jojo

[Joey Mack]

I forgot to add, to check the large ground bolt on the engine, in front of the starter..  the 2 thin eyelets are for the engine harness..

[JoeH]

Do you have any Engine Malfunction Light codes? Lightning bolt indicator should come on initially when the key is turned on. If not, fix that lightbulb so you know if you are getting a fault code.

If that circuit works and the light is on, with key on (engine can be running or off, doesn't matter) turn cruise control "off" then hold the set/accel / resume/decel rocker switch in the down position til the lightning bolt turns off. It'll then spit out a 2 digit blink code. Write the code down, hit the rocker again to request next code. Keep doing that til it loops and keeps playing the same pattern of codes.

[mjrays]

4 hours ago, Joey Mack said:

I forgot to add, to check the large ground bolt on the engine, in front of the starter..  the 2 thin eyelets are for the engine harness..

Where are those sensors located im new to these E7s

[Joey Mack]

Your engine is an E-Tech..  flywheel sensor is behind the starter in the side of the flywheel housing. The plug and wires can be seen running along where the clutch cable is.... The cam sensor is at the right front corner of the engine near the over board breather..  the cam sensor is called the engine position sensor. The one in the flywheel housing is called RPM/TDC sensor.. do you know where the fuse box is under the hood? Did you check the ground wires on the block yet?   All this is easy and free to do.

[mjrays]

4 minutes ago, Joey Mack said:

Your engine is an E-Tech..  flywheel sensor is behind the starter in the side of the flywheel housing. The plug and wires can be seen running along where the clutch cable is.... The cam sensor is at the right front corner of the engine near the over board breather..  the cam sensor is called the engine position sensor. The one in the flywheel housing is called RPM/TDC sensor.. do you know where the fuse box is under the hood? Did you check the ground wires on the block yet?   All this is easy and free to do.

I do know where fuses are ill check everything you said when I get back to it thanks for the info 

[JoeH]

Before you go digging all around, you really should update us on the functionality of the check engine light circuit. If either of those sensors are bad it'll light up the lightning bolt dash EML.

[Joey Mack]

It may be best for me to leave this thread.  Good luck sir..   Jojo

[mjrays]

25 minutes ago, Joey Mack said:

It may be best for me to leave this thread.  Good luck sir..   Jojo

Thank you for your help hopefully I'll have time Monday to work on it 

[JoeH]

59 minutes ago, Joey Mack said:

It may be best for me to leave this thread.  Good luck sir..   Jojo

Don't leave it, you know too much to do that. But he's gotta let us know if the EML light is working properly. I bought a 2001 RD vmac III once that someone pulled the lightbulb out to mask about 10 active fault codes. The blink code system is a great ally, if it's functional and hasn't been tampered with.

[Joey Mack]

all good,, just going to see the results of his diag..   

 

I tend to post post too much..  im training myself to ''chill''

[mjrays]

17 minutes ago, JoeH said:

Don't leave it, you know too much to do that. But he's gotta let us know if the EML light is working properly. I bought a 2001 RD vmac III once that someone pulled the lightbulb out to mask about 10 active fault codes. The blink code system is a great ally, if it's functional and hasn't been tampered with.

Here's what I'm working with I'll have to pull the dash and puts some bulbs in it I was hoping to work on it tonight but got hung up 

[mjrays]

Thank you for your help this is my first mack 688s been around truck awhile now picked this up short money was sitting about a year and half guy swears ran fine when parked (company closed up shit just sat ) 

[JoeH]

About 3-4 screws on that top piece of the dash above the rpm/mph gauges and you should have access to those 2 little lights in the center. Looks like one "fell out" (tampered with most likely). Light socket will be laying just inside, and I believe it should have a little tag on it saying what its for.  Get a good bulb stuck in the Engine Malfunction Lamp socket and turn the key to the "On" position. EML 'should' turn on briefly then turn off, indicating that the light works and there's no "Active Faults". If it stays on then you have active fault codes which can be retrieved by holding the set/resume cruise control rocker in the down position. Count the blinks to get a 2 digit code, write the code down and rock the switch down again to retrieve the next code. Post the codes here and Joey will straighten you out! 

One thing worth noting is ECU locations:

 The Engine ECU is located under the stainless covers below the turbo. This ECU is weatherproof, but there is a recall on the Coolant Level Sensor because the sensor can fail and let coolant wick along inside the copper wire and corrode the EECU pins. Not sure if this problem affected the early ETECH engines or just the later ones. Be careful when doing any mechanical work, that ECU can get pinched when replacing engine mount bushings or replacing clutch etc.  A small dent in that ECU and it's toast.

The Vehicle ECU is located on the kick panel in front of passenger's feet.  DO NOT drill holes into that panel without first checking VECU location. Idk why you'd drill holes in the panel but I hear it's been done before.  The VECU is not weatherproof, and rain water can leak through windshield gasket/firewall and get onto the VECU, frying it.

These are great engines and I think it's one of the best computer systems you can have on a truck because of the blink code diagnostics.  There's no need for computer software that costs thousands of dollars to find out what's wrong with it. In fact, Mack/Volvo released the diagnostic software for these computers for free, you just need to download it from somewhere like "DieselLaptops.com"  and buy a roughly $750 device that has the cable ends and interface device to link a laptop and the truck computer together. Diesel Laptops also has their own program 'Diesel Explorer' that is pretty good. It'll give you a lot of data, it'll tell you what ECU's are powered up/communicating, which helped me identify why I couldn't get my 2003 ETECH to start.  The EECU wasn't getting power, and I didn't know that til I couldn't see it listed in their software.

Edited November 30, 2023 by JoeH

[JoeH]

That is a nice looking truck, I'm a sucker for R models.

[JoeH]

If it doesn't already have one, it's worth putting an intake boost gauge on the truck at some point. The charge air cooler in front of the radiator cracks along the welds every once in a while. My E7-350 was only making 25psi boost and running hot on the pyrometer. Found cracked CAC, replaced, and now it'll push well passed 30, close to 35 psi boost. And much cooler EGT's.

But we'll sort out your current problems first.

[mechohaulic]

2 hours ago, Joey Mack said:

all good,, just going to see the results of his diag..   

 

I tend to post post too much..  im training myself to ''chill''

NO such thing as POST TOOO MUCH !!!!😱 ALL info is beneficial . even us ole bast--ds look forward to learning more from tooo much info. 

[Joey Mack]

Yeah,   I really can't stay away... Especially for an E-7/E-Tech issue...  I just don't want to stack too many things on at one time for someone who is not familiar with this setup...    Jojo 

[Joey Mack]

Here is a code list..  the code sequence is down the middle of the pages..  

V-MAC_Fault_Assignments.pdf