Category Archives: bus trouble

Replacing the IPR *or* No more Hot Start Fail!

So, I finally got to replace the IPR (Injector Pressure Regulator), in hopes of tackling the very frustrating Hot Start Fail problem that I’ve been dealing with on the bus’ T444E engine.  The IPR is attached to the base of the high pressure oil pump, between the valve covers and kind of under the fuel filter/water separator, and lots and lots of wires and air ducting.

The IPR is right where I’m pointing – between my finger and the white of the chuck pad.

In doing my research on changing this part, I found that I’d have to be prepared for some oil leakage from the high pressure pump’s reservoir, and that I’d need a deep socket to get the regulator itself out.  I had a chuck pad I could use (they’re really absorbent) and was able to slide it in under the old IPR to catch the escaping oil – though no quantity had been specified, just that I should “have a bunch of paper towels ready”.  I hoped I was ready.

The new, shiny IPR, disassembled.

The IPR is a solenoid valve, and the electromagnet comes off the stem that houses the moving bit to control oil flow.  So, to take the piece off, you first have to remove the holding nut, a spacer, and the electromagnet from the stem, which can then be unscrewed.
All in this very small place.

The IPR plug.

But it can be done, and relatively quickly, it turns out.  The electromagnet has an electrical connection for controlling it, and that just has two clips on either side, then slides out and can be woven back around some pipes and wires to keep it out of the way.  The upper portion of the plug is wider than the lower, so you can’t plug it in the wrong way – an important detail for putting everything back together and doing it by feel.

The 3/4″ wrench getting the holding nut loose.

The next thing is to take off the 3/4″ nut that holds the electromagnet and spacer onto the stem.  This is a very thin metal nut, so it doesn’t take much to get it off, but if your 3/4″ wrench is long (like mine), be prepared to make a bunch of very tiny pulls to get it finger-loose.

Electromagnet, spacer, and holding nut.

Once the nut is off, the electromagnet and spacer should come right off.  I ended up having to unscrew the spacer for a bit along the threads for the holding nut before it broke loose enough to slide.  And a little wiggling was necessary to get the electromagnet to slide, but it came more easily than the spacer once I got it wiggling.

The 1 1/8″ deep socket.

It was then time to get the deep socket.  In doing my research, I had taken the new IPR I had apart and fitted the stem to a large (shallow) socket that I had to find that it was a 1 1/8″ size.  Our local Autozone had a deep socket in stock for $8, so that wasn’t bad at all to get the right tool.  However, the stem is so long that you need every bit of space in the deep socket (I wasn’t sure that the ratchet end would sit in the socket securely), and it turned out that the deep socket’s center hole wasn’t a full 1/2″ in diameter, so it wouldn’t fit the stem up into it.  And of course, that would mean that the socket wouldn’t engage the points.  Luckily, I was able to use a 1/2″ drill and get the hole open so that it would work.

Deep socket and ratchet in place to remove the IPR.

Then there was just the matter of getting the socket onto the stem, which involved some wiggling, moving of wire harnesses this way and that, and then, once on, doing some more of it it get the ratchet down to engage it.  For this, I ended up using the 3/8″ ratchet with a 1/2″ adapter on it to be able to get a better pull, as well as to get a spacer between the socket and ratchet that was long enough, but not too long, to work around hard engine elements.

The old (and somewhat blurry) IPR is all out!

The stem broke loose fairly easily, and with some wiggling and shifting, it came out!  I could see that the chuck pad had collected some oil, but couldn’t see how much at that point.  But the important step of removal was now complete.

The new IPR in place!

I transferred the protective red plastic cap from the new stem to the old one, and set about reversing the process to install the new IPR.  The only real difference was that as I was tightening the new stem in place, I slid the chuck pad back away from the high pressure oil pump, so it wouldn’t have a chance of getting caught and messing up the seal.  Once the stem was nice and snug, and the electromagnet, spacer and holding nut were on and secure, I plugged the control wire back in.

Easy clean-up for the planned oil spill.

In cleaning up, I checked out the chuck pad.  It looks like there might have been about 4-6 oz of oil that drained out when the stem came out of the pump.  I don’t know if that’s typical, but it’s my best estimate.

Once all the bits were stowed away, I started up the bus.  It cranked without starting at first, but knowing that it would have to pull enough oil to the high pressure pump before it would start, I kept it cranking, and then it caught.  It ran rather ragged for the first half-minute, then smoothed out pretty well.

Note the missing bit of green gasket at the bottom of the stem!

The new IPR is more responsive than the old one, but some of that could be  in the fact that part of the seal on the bottom of the old IPR was missing!  I’m wondering if that, coupled with either less viscous hot oil, or perhaps some dynamic of the metal being heated was what was causing the hot start fail.

At any rate, a quick test-drive, then attempted restart of the engine proves that the engine now starts up fine when hot.  It also seems a bit more responsive to the accelerator pedal, so I have to get used to starting off in second all over again.

Hot Start Fail

So, we had a nice day, and I decided to take the bus out for a test-drive.  Well, a test-start, really.  I figured that I should try and document what was going on, as I had read the last  service paperwork (where they couldn’t replicate the problem after it got towed) more closely while cleaning up on the bus.  The way it reads, they were looking for a hard start, but proved that the bus would repeatedly start when it was cold, and wouldn’t quit once running, which wasn’t the problem.

So, I videoed the cold start before a quick trip, and the attempt to start it hot that failed.  (Caution, it’s a bit jumpy at parts, as I had a webcam that I was holding in my hand to take pictures at times.)

This really shows the difference, and how the engine started/didn’t and how it sounded, mostly for my own reference, and to possibly take into the dealership to show them.

But in putting it together and watching it after I had uploaded it, I noticed how low the oil pressure was (I had been looking at the temperature, not the oil pressure).  While I had asked the mechanics at the dealership if the pressure was too low before, and they assured me that it was fine, this looks really low.  And since one of the things about that sort of non-start is the IPR (Injector Pressure Regulator) failing, so the injectors don’t get enough oil to function, that could be it.

Unfortunately, there’s also a possibility that it’s the whole High Pressure Oil Pump, which isn’t thrilling.  So, the next thing is to replace the IPR, and see what that does.




After the tow … An exploration in a hot bus engine not starting.

So, in January, there was a nice, (relatively) warm day that I decided to take the bus out and fill up the bus’ fuel tank.  The drive down to the Rez was uneventful, the bus was driving nicely, and all was well.  I pulled up to the pump, shut down the bus, filled the tank, turned the key, and the engine spun.  It spun way too easily.  And it never caught.

Perplexed, I let it spin for twenty seconds or so, then stopped and waited a minute before trying it again, only to get the same result.  After about 10 minutes of waiting and trying to start, I’d run the batteries down.  Luckily, we have AAA (with RV), so I called for service, hoping I could get (at best) a jump-start, or barring that get towed to the dealership back in Buffalo.

After it started to rain and the tow driver (Justin or Jordan (Sorry!) from Bach’s Towing) arrived and sized up the situation, we found that we just couldn’t get sufficient juice from the tow truck to start the bus, so it got towed back to the International dealership (Regional International) where I get all my inspections and service done.   After them charging it and checking it, it started up right away, and continued to do so every day they checked.  One of the mechanics drove it around a bit, and it started after that too.  They just couldn’t replicate the problem.

The IDM, mounted on the firewall behind the engine, with the cover off.

They found an error message about a missed toggle in the IDM (Injector Driver Module), but it didn’t show up again.  And, as the IDM was an expensive unit, they didn’t want to replace it if they weren’t sure it was the problem.  This unit takes the 12 volt power and ups it to 115 volts(!) to control the operation of the fuel injectors.

So I went and picked up the bus from the dealership, and drove it to a local park (Chestnut Ridge Park, which was still fairly close to Buffalo in case things went really badly) so I could have some time to myself, and it didn’t start again. My hypothesis was that if the engine was fully up to temp (up around 180 degrees on the coolant), that was when the problem happened. So, I decided to wait half-an-hour and THEN try to start it.  After the wait, it started up fine.

The Eternal Flame at Chestnut Ridge Park

I drove it around inside the park a little to the head of a hiking trail, getting the engine back up to temperature (~180 degrees) and after shutting it down, it again wouldn’t start, it just spun.  After a hour-long hike, though, it started up great.

As the dealership had not been able to replicate the problem, and I had replicated it twice in the space of an afternoon, I was a bit annoyed.  So, I took to the internet.

It seems that there are three major issues with the T444E that can cause the ‘spin but not fire’ starting issues.  The first is the IDM, which, when it fails to send power to the injectors at the behest of the ECM (Electronic Control Module), the engine gets no fuel.  The second is the IPR (Injector Pressure Regulator) which is a solenoid valve to control the high pressure oil feed.  The third is the CMP (or CAMP) (Camshaft Position Sensor)  which notes a certain slot pattern on a camshaft disk which indicates that cylinder 1 is in the correct timing position.

Any one of these failing can get the ‘spin but not fire’ situation.  I could also get that if the fuel filter was clogged, but then it wouldn’t start when the engine was cold either. So, at any rate, the parts were ordered from Shop Injectors and updates are to come.