Hi guys!
I'm making myself dizzy with the search for help on my issue. Hoping I could get some direction as half of my livelihood depends on this vehicle!

Here's the rundown:
last November had to replace the IP due to it leaking from the rotor/head. Also had some leaking injectors/o-rings

Replaced all bad injectors and all o-rings and IP. This was the beginning of the new problem....hard starting only when hot.

I own a mobile dog grooming business using this 93 E350 7.3 idi with 180k on the odo. When we start it in the morning, it fires right up, less than 2 seconds, starts and idles perfectly. Runs perfectly to the customer's house. Customers are typically 15-20 minutes away from the lot. We service the dog (about 75-90 minutes) and the motor will not start for at least 5 minutes but usually 20-30 min and sometimes up to an hour.The time it takes to start seems to take longer and longer the later in the day it gets. Also depending on ambient temperature. 100* outside basically means we won't be able to start the bus until it sits for an hour or 2 (past the finish time of the appointment).

Here is what I have done to remedy the situation (this started right after the IP was replaced).
Replaced the new IP with another IP (then replaced that IP with a 3rd unit)
re-routed windshield washer hose to direct water spray onto the IP (until very recently, this somewhat worked actually)
Replaced 2 other injectors that were found to be leaking
Replaced 5 bad glow-plugs
Whole new set of o-rings
replaced 2 fuel lines that were "bent"
Filter housing gasket (around the sensor)
Replaced starter, Batteries, vac-pump, radiator hose (burst).
Replaced mechanical lift fuel pump with electric pump
It has (in the past 10 days) developed a strong wobble (lope) which led me to think I had a bad cylinder or injector or motor mount (wobble evens out at about 30 MPH)
Large volumes of Black Smoke on downshift continuing until OD engages again, but not above average smoke on normal acceleration.
Relative compression test- Failed


Also replaced:
AC Compressor
Transmission (E40D)
Neutral SS
Shift Column Tube


Most of the work done has been done at the Ford Truck Dealer local to me and I am very frustrated with their results as this is still occurring and I've dumped $$$ into the problem.

I am fearful that the motor is dead at this point and wondering if anyone can point me to a line of investigation or solutions. It's currently out there working, my groomer just leaves the motor running all day at this point, which is only going to exacerbate the problems.
The temperature is what perplexes me. If I want to short-cut the waiting period to start it, I can open the hood for a few minutes and put some cool water on the IP and it will usually start up after a few 5- 10 seconds of cranking.


Any ideas? Getting desperate at this point...shopping for rebuilts, used motors etc....

Thanks in advance!

 

Wow! I am sorry to hear that you have had all this work performed, at a dealership, and you still have problems and no answers.

I think the water on the IP trick typically indicated your IP was bad; I do not know. If your relative compression test failed, I would think this is most of your problem since diesel combustion is dictated by compression. Assuming, you have no air leaks in the fuel system, your harder starting, when warm, is probably due to compression issues- and since the glow plugs only work at lower temperatures, you crank and crank and HOPE for ignition. You could perform a manual bypass of the glow plugs, when warm, to see if the truck will start quickly- this will only buy you time because you need the higher compression.
As far as your failed relative compression test is concerned, did they offer you a mechanical compression test, afterward, to determine the actual compression and if the low compression (assumed) is due to rings or valves? In the meantime, I would look for another shop. It seems your shop has left you with more questions than answers. After this test, do they intend for you to solve the issue yourself?

 

Taking it right from the top:
1. If it starts cold, you've got enough compression to do the job. Honestly, even if you have one dead cyl, it will still start. I wouldn't worry about the dynamic compression for the starting problem.
2. If pouring cold water on the IP makes it start hot, well, you've narrowed that problem down. It is, at that point, 100% the IP.
Where did you get these "new" IPs? There are a lot of cheap shops which rebuild these IPs, but don't want to replace the rotor due to how expensive it is. Having new injectors will only make this problem worse -- the higher pressures make it harder to start.

In addition, you always want to replace injectors all at once - even slight variations in pop pressure massively affect how the engine runs, and make it hard if not impossible to time it correctly.

 

Well, it was a family friend that offered to check the compression for me (I've lost trust for just about everyone else) and his shop isn't really setup for major commercial vehicle repairs. He had nothing to gain/lose with the diagnosis. I guess my question is: failed compression is failed compression, in the interest of time vs. money should I be looking at replacing the motor or rebuilding? Should I continue diagnosing? Does knowing it's cylinder-X make much of a difference in the next step? I just keep hoping something relatively easy is being missed as the whole situation hasn't really gotten any worse but also wasn't showing any signs of the problem before the original IP replacement and it started exactly at that juncture...alas...bad compression is an issue.....

 

The IP's are from NAPA, Borg Warner is the re-builder (apparently there are very few (3 I think) national re builders) I just figure that the chances of 3 bad ones would be very slim (although possible I suppose). The cold water deal only works some of the time....and much less as the ambient temps are higher...The injector issue I was not aware of....but you think that would be enough of a difference with the temperature? Wouldn't that always affect the start?

 

Maybe my reply was a little harsh; I apologize. Yes, and thank heavens for family and friends who help out in any way they can. I would see if your friend can do the compression test to check the rings and a dry air test to check for blow by and valve seating. You could offer to purchase the tools, maybe from Harbor Freight, so his expenses are kept at a minimum. You need the compression test because the whole operation of the engine depends on it- sort of like a heartbeat or blood pressure reading. Once you absolutely have the compression and if the valves are seating properly, you limit the number of other items, such as fuel, timing, and air for combustion, which can be the problem. If you know for certain the pump us good, fuel system is good, including tank pickups, injectors, etc. you are 2/3 through your problem.

Edit: I would try bypassing the glow plugs, if they work, when it fails to start when hot/warm. Use them for just a second or three. This procedure should supplement a startup due to lower compression issues. This is not a permanent solution, but part of a diagnostic process that should help.

Good luck. I'll try to help as much as I can. Keep us posted.

 

Can you post a video of it cranking and trying to start? Perhaps one of it running? Videos help diagnosis by far.

You say the relative compression test "failed"... What were the readings? 0 on 1 cyl? Or just 50 psi lower? Or...?

I'd not write the engine off yet. It's too easy to get a poor reading when checking compression if you didn't tighten things down /quite/ right. It's also less important than it seems - look at the 'service limits' for the 7.3; the allowable compression range is /huge/. You'd /like/ them balanced, but that's not stopping it from starting.

 

A relative compression test doesn't actually measure compression. You measure starter current draw while cranking the engine several times. The THEORY is that if compression is low on one cylinder, the starter won't have to work as hard cranking the engine past that cylinder's TDC point between the compression and power strokes. So a graph of the current draw will show an irregularity every eight cycle, rather than a nice even up-down zig-zag graph.

But it's obviously just a guesstimate. An anomaly in a relative test means that an actual compression measurement test should be done. THEN, if a particular cylinder does show lower compression, a leakdown test on that cylinder should be done.

 

Can you point me to a thread or youtube for the bypass procedure? Is it relatively simple? This will help confirm the compression issue, or simply just get the starting issue fixed for now??

 

Oh, that makes sense. So it could just as easily be a shot pair of brushes or dead winding in the starter, if you didn't have a "trailed eye" looking at the graph?

 

Bypassing the glow plugs (relay) is not going to fix a compression deficiency. Bypassing the relay and using the glow plugs, may help your engine start faster, due to raising the temperature in the cylinder. You do not want to rely on this method for operation. Try this method as a diagnostic tool in the absence of the compression test. The best choice is to get the compression test so you are not chasing "ghosts" - that term really scares me.

It looks like (verify first) power is applied to the ignition terminal to power up the glow plugs through the relay.

1Main page Pre-Power Stroke Diesel (7.3L IDI & 6.9L) - Ford Truck Enthusiasts Forums
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Good luck

 

Yeah, I don't like this process either. It makes sense that ampere draw will be highest on the compression stroke, and all cylinders should look alike. By looking at the graph, one could determine what percentage in varied pressure is acceptable, as per spec's. A good starter or efficient starter could have a lower ampere draw, as compared to others, and give a lower reading across the diagnostic screen- but all cylinders should be relatively low within the allowed percentage - implying that all cylinders are low. Now if the starter is good and the ampere draw indicates the cylinder compression is all over the board, it could indicate compression abnormalities.

The compression and leak down test should be performed. The compression is dependent on the proper operation of the valves. I worked on a Ford gasser that was just out of warranty (time). The engine was replaced with a factory unit and had about 17000 miles on it. The technician condemned the engine because two of the cylinders had zero compression. I THINK the tec's did an actual compression test, but neglected the leak down or air test. I found two of the pushrods bent, and holding the valves open. The pushrods, @ about $14 each were from Mexico and half the weight of the replacements. Long story short (please! ) both tests are necessary.

EDIT: Conversely, a worn cam lobe, worn lifters or worn rocker arms could prevent the valve from opening fully, which would cause lower compression readings.

 

Sorry for the delay, I didn't see the additional responses and I actually really appreciate the help....
Ok, I am seeing that I need the actual compression test...but at any rate I'm at least talking about taking the upper engine apart (bad valves)...bad rods would mean the lower engine needs to come apart too right? This is my commercial rig, making money every day its out and losing money every day its not out (it's currently on the road making $$ but surely won't last much longer)...do you all suggest the tests to determine the best next step or will spending the diagnostic time (and $$) basically mean the final result is rebuild or swap anyway or do you feel like it might lead to an easy fix??

I just need to get this resolved as fast as possible with a eye for durability and cost (aren't we all looking for that? :-) ) Unfortunately most of this stuff is above my pay grade, I need a shop to do this work.

I'm leaning towards rebuilding to just get it handled. Is rebuilding less expensive than a swap? Got a quote yesterday to swap in a factory rebuilt from ford for $12K! That seems WAY high but maybe I have the wrong expectation about the cost involved here.


Can anyone suggest a reputable shop around Modesto CA? Google has failed me in that regard!
Of course

 

My comments are inserted into your quote below

 

^^^^^ +1 on STARTING with the actual compression test, and then if needed a leakdown test. Speculating on what it might need before the tests, and esp. thinking about a rebuild, is like imagining you have appendicitis on your way to the doctor's office when you have a little stabbing stomach pain. You're jumping way too far ahead. Get the tests done, regroup and re-assess.