Two 7.3's kickin my A$$

CLR95 · January 30, 2008

Well I just thought I would post on here and see if you guys have any other ideas other than what I am thinking. The first truck is a 97. Brought in for fuel gelling issue. Checked everything out changed filters let truck sit out in cold for a day and it ran fine. Customer was on the way to get the truck started the truck let it idle (well my SW did start it anyways) said the truck got real loopy and then died. Now there is no wait to start light water in fuel light nothing. Truck cranks just no start. Went through all the fuses found nothing. Have no communication with the PCM through the genstar. Went through pinpoint for no communication and it has lead me to replace the pcm. Now is there something I am missing. I have doubled and triple checked everything I can think of and still nothing. Am I on the right track with the PCM?

Case number 2. 00 truck used for a tire repair facility. Truck does not get serviced as it should. Problem is it will not start when cold. Even in a heated shop over night if not plugged in the truck will not start. So i go through the basics oil is nasty black changed that, haven't checked the fuel filter, glow plug relay works, batts are junk, did an amp draw on the glow plugs and they are pulling 180, checked gps through harness and the highest reading was 1.2 ohms. It does have a cylinder mis firing but I don't think it has anything to do with it not starting. Now tomorrow I am pulling the v.c.'s off and gettin a closer look. Plan on checking the gp's individually to make sure resistance is within spec. Have also thought about running a compression test good idea? It smokes white during cranking just no heat to light it. Anything else I should look at while I am in there. I think I am on the right track and have been thinkin bout what Jim says in understanding what is going on and why and how and just curious if anyone else has any input... still green in the game but am trying to learn all I can... thanks guys and sorry for the book.

Jeff_ · January 30, 2008

In regards to your first one, DONT REPLACE PCM untill you check VREF. should be 5v. If any sensor (like EP) is shorting vref to ground (which is common) you will lose communication and glow plug light.

Jeff_ · January 30, 2008

In regards to your second one, a few ideas come to mind. I would first put good batteries in it because cranking speed is important. Since you mentioned that this vehicle has been neglected, it is not beyond the realm of possibility for it to be dusted and therefore not capable of creating enough compression heat to light. This theory would be consistent with your misfire and smoke concerns. A quick and easy check before digging in too deep is just run the engine with the oil cap removed. If you get a strong huffing smokestack from the oil filler, it can only come from one place-blowby. If you find this, then yes, by all means perform crankcase pressure and compression tests. In my experience it seems cyl 8 usually gets dusted first, and you will usually notice sand blasted turbo fins as well.

Another thought is injectors. Perform a buzz test and use your ears. They buzz in numerical order 1-8 and if you notice 1 that is muffled compared to the others it is usually a sticky spool valve from contamination. If you end up going down this path it would be a good idea to bench test all injectors with the rotunda vacuum test fixture, and replace or reseal as necessary.

I'm getting ahead of myself a little though. Make sure you don't forget the basics: check Fuel pressure, check weather the hp pump reservoir is leaking down overnight by removing the inspection plug in the top and checking the level-if its low we can give you further advice, What is the ICP pressure and IPR percentage when cranking?

It's late so I'm going brain dead, Let us know if you need more ideas, or what you find. There are a TON of knowledgeable experts here.

Jim Warman · January 30, 2008

The PPT for your no communication is telling you to use a voltmeter to verify open circuit voltage to the PCM.... this is inappropriate test number one.... A poor connection can flow enough current to satisfy the needs of the volt meter. This test method is bogus.. you might as well just measure B+ and be done with it.

This same PPT will likely have you test the ground with an ohmmeter... same deal... bogus test.

The only way to test either a power supply circuit or a ground circuit is with a load... I still rely on my trusty sealbeam headlamp... Bruce has an electric motor that draws about 9 amps... easily twice what the lamp draws... the electric motor is better.... the lamp is *usually* enough.

Grounds get the same treatment... if you aren't going to load test... don't bother testing.

FWIW, if you install the breakout box, you can now do a proper voltage drop test with the circuit "live" and in it's natural state.

If you have no wait to start lamp, no start and no comm on a 99 and up - it is usually a shorted fuel heater and a blown fuse.... Read the circuit diagrams... spend some extra time learning what all the little dashed lines and sqiggles mean... Added bonuses in the circuit diagrams are the "power distribution" section (allowing us to see everything in each fuses branch) and "harness overview" showing the routing of each harness.

One last word to the wise on truck one.... I've been caught too many times (and seen too many techs caught time and again) by checking every fuse in the truck... we can be left not checking a fuse that is MISSING....

Something to remember... every PPT ends in replacing a module... After we replace the module, we discover the bogus test procedures. Read each test step carefully... decide what the test step is really looking for... and test it appropriately (meaning "as if it were in daily use").

Truck number two... three words..... "no start PIDs". V_REF, RPM, IPR, ICP (the volt reading is the important one), FUEL_PW (if available). I think I might be missing one but there is a very good diag sheet for no-start in the PC/ED. I don't like the order that things are in, and I shuffle and change them around for individual circumstances... but I always go with the least intrusive test first.... Nine times out of ten, well start with a KOEO test... since we have everything hooked up and initialized, might as well get the PIDs out of the way at the same time.

A lot of guys put a lot of faith in a glow plug draw test... For the small extra time, I'll ohm the GPs at the valve cover gasket, thank you.

You have smoke out the tailpipe while cranking, so we "should" be able to "safely" rule out any fuel supply or ICP problems. This choice is going to be a matter of taste... If you decide to bypass one step in favour of another... be prepared to back up if the direction you chose doesn't seen "right". If you're really green (and I don't mean that as an insult - every last one of us started out green as grass), I suggest doing all the tests in Fords sequence until you get a comfortable familiarity.

But you have smoke while cranking.... until we decide going another direction is a bad choice, we can ALMOST safely assume that we have ICP, CMP and fuel. Like Jeff said... time to look at cranking rpm... 150ish... maybe up to 180ish would be in the neighbourhood... Too fast and we might have a cylinder sealing concern. Too slow and it just ain't gonna go.

A this point, the obvious choice is to check cranking rpm... and that will decide our next step.

Sidebar - There isn't an electrical test out there that can compare with a properly performed voltage drop test.... (let's not get into sensor patterns here... that's a whole 'nother game). A properly performed VD test starts with checking B+ with the key on or off as the test procedure dictates to establish a baseline. I like to trickle the batteries to help maintain an even B+ through-out the procedure.

CLR95 · January 30, 2008

Truck #2: I forgot to add that I was looking at the pids while cranking. IPR comes up to over 40% and icp is in the 2300-2400 range and rpm is around 150. And mind you it acts like it wants to fire you here a few cylinders hit and hit before it deciedes to run. I did put new batteries in it this morning. Truck sat in the shop and it started still had no power as if there isn't any heat in the cylinders. I did test the glow plugs at the harness and they all checked good highest reading was 1.3 ohms. Going to check crankcase pressure and compression after lunch. Also while checking compression I might check each glow plug individually to double check they are ok.

Truck #1: I completely neglected the thought of the fuel heater shorted. I will get it back in the shop and take a look at it. I will recheck the fuses and see if any are missing. I have been burned by a pinpoint before Jim thats why I don't feel confident its the pcm. I have one of the way but I am going to check other things in the mean time. VREF was low if I recall don't have the sheet in front of me that I wrote all my stuff down on. Thanks for the words of wisdom Jim with experience comes more thorough diag's and I wish I had both but for now I am learning as they come. Thanks again

Keith Browning · January 31, 2008

Chris, did you take a fuel pressure reading and a fuel sample?

Bruce Amacker · January 31, 2008

If you have no wait to start lamp, no start and no comm on a 99 and up - it is usually a shorted fuel heater and a blown fuse....

Weird- I've never seen this on a '99 up, but plenty of times on Gen 1 trucks. They redesigned the heater on Gen 2s to help prevent this.

One last word to the wise on truck one.... I've been caught too many times (and seen too many techs caught time and again) by checking every fuse in the truck... we can be left not checking a fuse that is MISSING....

I won't tell you about the 3 DAYS one of my techs spent on one of these. /forums/images/%%GRAEMLIN_URL%%/smhair.gif

A lot of guys put a lot of faith in a glow plug draw test... For the small extra time, I'll ohm the GPs at the valve cover gasket, thank you.

I challenge you to a GP diag test- you ohm the plugs, I'll amp them. We'll see who wins. /forums/images/%%GRAEMLIN_URL%%/grin.gif Aren't you forgetting voltage dropping the relay? Put a case of Molson XXX on it?

Like Jeff said... time to look at cranking rpm... 150ish... maybe up to 180ish would be in the neighbourhood... Too fast and we might have a cylinder sealing concern. Too slow and it just ain't gonna go.

150 minimum cold, and they crank about 177 warm. The frigging book says 100rpm, which is a joke.

My bets on this truck:

Low GP amperage (should be 195 initial, dropping to about 125 after 15 seconds. It's not your hard start problem if it's at least 140 or so)

Poor quality fuel

Poor injector spray pattern.

If the GP amperage is good and FP quality/pressure looks OK, drain the FF and fill it with Stanadyne Performance Formula (PM-17A). If it runs and starts better, it's a fuel or injector problem. Use a process of elimination to figure out which.

Good Luck!

/forums/images/%%GRAEMLIN_URL%%/grin.gif

Jim Warman · January 31, 2008

Bruce... something I can be notorious for is "missing" steps... not in my diag... but in describing my diag... Volt dropping the relay in my description is one of those things I forgot to mention because it's an automatic thing for me... I do it without thinking about it... let's not forget that this part is a three step affair... baseline B+ with the GPs turned on, drop the relay at the posts and drop from the feed battery to the relay hot post....

I have no empirical evidence as to why not check glow plug current... it is simply my preference to ohm each glow plug individually. If GP current isn't where it should be, we're likely going to wind up doing it "my" way somewhere along the line, anyway... (let's not lose sight of the fact that if we open the dictionary to "curmudgeon", there is my smiling face... complete with twitching moustache).

As for the fuel heaters... I've done a few on '99 up... all with the tall skinny fuse box rather than the wide fuse box (I still have trouble remembering that the GEM "died" at the beginning of MY '02). Like the older trucks, this still gives a blown fuse 30 and all the other symptoms....

I wont pretend to "teach the teacher"... but I prefer to say "I haven't seen <that>, yet" rather than "<That> never happens"... If I have no WTS light, crank/no start and no comm - it is much easier to check fuse 30 first than it is to install BOB and check powers and grounds (or even simply undo the PCM connector) if I find no V_REF (and I'll wager that you check V_REF first at the EBP???).

I'm a tactile kinda guy.... someone comes and says "my left rear turn signal doesn't woork...". It's time to check ALL of the lights... check the turn signals with the park lights off.... and then again with the park lights on... (Can anyone tell me what I'm checking with the second test?).

I don't think that you and I are doing anything drastically different.... but your experiences and my experiences may differ (simply because no two areas have truly identical conditions). Sometimes we amaze ourselves.... and sometimes we just pray that someone else doesn't notice our errors in judgement.

CLR95 · January 31, 2008

Alright... checked crankcase blowby visually and it has quite a bit. Gonna run the test first thing in the morning with the gauge. Pulled the rs vc off as cyl 3 is where I found my mis fire. Started truck and noticed the injector spitting oil as if it was possibly working. Won't know 100% til I pull it. I did notice this morning when I started it cold even though in a heated shop pedal to the floor it wouldn't get over 1200rpm thought that was very odd and it took a long time before it got any better. Obviously the more heat in the cylinders the better it ran. I will check fuel in the morning. The fact these guys last changed there oil in July of last year which was only 5k on the odometer but the truck runs all the time as it is a tire service truck and doesn't help my situation at all. So after I get all the basics checked worse case scenario head needs to come off for a closer peak at what is going on if it is in fact a compression issue. The misfire is obviously real bad when cold but still there when warm. So I don't know I am working on it thanks for the help guys. This is a learning experience to say the least and I feel way more comfortable with the 7.3's than I do with the 6.0's.

mchan68 · January 31, 2008

If this helps any, the last 7.3L that I had, which had a shorted out fuel heater, also got a replacement engine harness. The wiring had melted to the point where metal strands were exposed. This must've taken the PCM out as well. The "check engine" light would come on, and stay on, at key-on. As soon as I replaced the PCM, the "check engine" light would come on for about 10 seconds and turn off. But more importantly, the "wait to start" light would also come on, and the truck would fire up right away. This was on a 2000 E-450, if this helps any. The customer was only too happy to have the truck back and running. But when he came in two weeks prior to that, all readings were well within specs, with no DTCs or anything to indicate that there was a problem. Some "meat cutter" had plugged off the water separator drain with a section of rubber hose, a bolt and two worm clamps, eliminating the drain altogether.

Keith Browning · February 1, 2008

Weird- I've never seen this on a '99 up, but plenty of times on Gen 1 trucks. They redesigned the heater on Gen 2s to help prevent this.

Bruce, I have seen this, once. I repeat, ONCE. I could not see anything wrong with the heater so it must have been one internal because like you said, the heater was redesigned and quite effectively because I have not seen any fuel heater issues on a 7.3L in years now. I do have a story about a 6.0L Econoline fuel heater though - I will be updating a recent article shortly, bear with me.

Bruce Amacker · February 1, 2008

I do have a story about a 6.0L Econoline fuel heater though -

I have nice pics of a broken 6.0 F-series fuel heater I found by accident. We changed the pump for a different problem and on teardown the heater was broken in half with no symptoms.

/forums/images/%%GRAEMLIN_URL%%/grin.gif

Jeff_ · February 6, 2008

CLR95, Have you determined anything for sure on either of these yet?

CLR95 · February 8, 2008

Yea they are both up and rolling. Had a dumbass attack with the 97 checked the fuses again and found the fuel heater blown and changed the fuse and heater all good. The 00 had a fuel issue. Fuel Filter was pretty nasty so changed that added some additive to fuel bowl and tank and had my sm drive the shit out of it. Let it sit outside for two days and she fired right up. Still has a slight miss but runs way better than it did before. Thanks for the help guys chalk up another learning experience for me.

LARRY BRUDZYNSKI · February 9, 2008

If you learned something from these 2 trucks and they are down the road then they didn't kick your ass you kicked theirs. /forums/images/%%GRAEMLIN_URL%%/cheers.gif GOOD JOB

Keith Browning · February 9, 2008

Originally Posted By: Bruce Amacker

Weird- I've never seen this on a '99 up, but plenty of times on Gen 1 trucks. They redesigned the heater on Gen 2s to help prevent this.

Bruce, I have seen this, once. I repeat, ONCE. I could not see anything wrong with the heater so it must have been one internal because like you said, the heater was redesigned and quite effectively because I have not seen any fuel heater issues on a 7.3L in years now. I do have a story about a 6.0L Econoline fuel heater though - I will be updating a recent article shortly, bear with me.

Had one show up last week I did and didn't realize the fuel heater was involved thinking that the heater was revised. Nope. This 1999 truck had the old style heater, and yep, the anchors were rotted away. Coincidentally, the replacement part was the revised style.

LARRY BRUDZYNSKI · February 14, 2008

Sucks when one jumps up and bites you in the ass. /forums/images/%%GRAEMLIN_URL%%/banghead.gif

BLittle500 · January 14, 2010

I just ran into a truck like "truck 1", 2000 7.3 no wait to start light/no start. Pulled the filter housing and sure enough the heater was junk. Got the new one in (which was updated) and away she went.

I know it's an old post, but no point in making a new one. This is the post that helped me figure out my truck, not alot of experience on 7.3's yet, so I keep coming back here for info.

Thanks again guys,

Brandon

DamageINC · January 14, 2010

I had a 99 no-start with the same problem once also, shorted fuel heater taking out the fuse. I still haven't seen another one since then and that was probably 3 years ago.

Dave