New DP owner 3126B died - need some help

[csracing]

Hello everyone.


We purchased our first diesel pusher on Friday. 1998 National Tradewinds with a 3126B Cat engine. The coach ran like a top 3/4 of the way home (about 1.5 hours of runtime) and then it went into limp mode and we had to pull off the highway and start diagnosing. I was able to limp home and since parking the coach I have not been able to get it started.

I pulled codes: 15 and 39 are prevalent.


I have some high pressure hydraulic gauges so I removed the HEUI pressure sender and connected a gauge. I'm seeing about 200psi of pressure when cranking. The engine cranks over plenty fast. I went through the Cat diag steps that I could find online without getting the engine to restart or smoke out the exhaust so I'm pretty sure the HEUI pump has failed.


Just looking for other ideas or steps that need to be taken before I pull the trigger. I do not have access to a scan tool.


I'm very handy and have been building engines and transmissions for a long time so the work doesn't bother me at all.


Thanks in advance for any advice/help.

We can't wait to finish cleaning up this diamond in the rough and putting some miles on with our next adventures.

[Skip426]

Welcome to iRV2.

Sorry your first post is about problems .
Here are a couple of pdfs on the operation of our Cat 3126Bs .
First one has the code list.
200 psi oil pressure cranking does sound low , I'd expect 800.

[wolfe10]

Two much less expensive things you might check:


Pull the primary (or only) fuel filter and check for algae, debris or AIR in the filter.


Air, from a vacuum leak into the fuel system anywhere before the HEUI pump can result in a no start/poor running. Putting a short length of clear hose before the pump will show you if there are air bubbles in the system.

[bizzerbiz]

Most definitely replace your fuel filters. I have the same engine. Last year in Montana, I started having hard starts, then no start. I replaced the filters "which I had with me" and it started up and hasn't been a problem since.

[hex nut]

The '98 Tradewinds has two fuel filters, primary and secondary (primary is also the water separator). If this motorhome sat for any time at all before you purchased it, it is very likely that you have algae in the fuel and you ran it just long enough for that algae to totally plug up the primary fuel filter. The primary fuel filter/separator is in a bay on the drivers side. The secondary fuel filter is on the engine accessible under the bed. Change both of them before you do anything more expensive (and always carry spares). Be sure to prefill the filters with clean fuel (or ATF) before you install them. The filter on the engine may have a primer hand pump, some do some don't. I had this exact experience when I bought a '98 Tradewinds years ago. It is an excellent motorhome, enjoy it for a long time.
Good luck.
Richard
P.S. Always use CAT filters for the secondary filter on the engine (not so critical for the water separator). HEUI motors require clean fuel and clean oil and only CAT filters are built to the exacting spec's required.

[ftodaro]

There is a check list for no start posted on line. Generally its either fuel or the ECU. I would do the low hanging stuff first. there is a fuel pressure regulator at the back of the head that you can tap into to see what type of fuel pressure you have from the lift pump. should be in the 30 to 60 psi range i think. I had a buddy just face that issue, it was the hand pump on the fuel filer assembly. I would get the list and go through it.

[csracing]

update. Replaced the HEUI pump, pressure regulator and both fuel filters. Got it started and running. Haven't tried to drive it yet. Have active codes 72, 73 and 74 now which I read are injector drivers. Anyone seen this before? Is it a dead ECU and if so does it make sense that it would start and run with bad injector drivers?

[Dunrollin]

I had something similar on my injectors, I can't remember the codes it threw. I took it to Caterpillar where they diagnosed it as Injector #3 not firing and found a faulty wiring connector.

Simple fix for that one.

[Rkesselus]

Originally Posted by hex nut

The '98 Tradewinds has two fuel filters, primary and secondary (primary is also the water separator). If this motorhome sat for any time at all before you purchased it, it is very likely that you have algae in the fuel and you ran it just long enough for that algae to totally plug up the primary fuel filter. The primary fuel filter/separator is in a bay on the drivers side. The secondary fuel filter is on the engine accessible under the bed. Change both of them before you do anything more expensive (and always carry spares). Be sure to prefill the filters with clean fuel (or ATF) before you install them. The filter on the engine may have a primer hand pump, some do some don't. I had this exact experience when I bought a '98 Tradewinds years ago. It is an excellent motorhome, enjoy it for a long time.
Good luck.
Richard
P.S. Always use CAT filters for the secondary filter on the engine (not so critical for the water separator). HEUI motors require clean fuel and clean oil and only CAT filters are built to the exacting spec's required.

x2 Exact same problem Algaecide changed both filters every 750 miles twice and then at 2000 more. Probable could have been faster if I chose to drain the tank. That was 4 years ago and 45,000 miles ago. Hope you problem is as simple. Richard

[gatorcq]

I would start with replacing just the IAP Sensor. Cost $160, plus 1 O'ring. many shops and owners wnet with the Pump only to find the sensor was the problem. Call CAT, order a sensor ask for the paper showing location.

[csracing]

More updates to this post. I replaced the IAP sensor and both fuel filters before I drove the coach. It would start but ran in low power mode so it was pretty underwhelming to drive. Since I had injector codes and everything I've read say the ECU needs service, I sent the ECU off to be repaired. Service facility replaced some failed capacitors related to the injectors. Got the ECU back and the engine started up pretty much the way it always has. Test drove it but it still had very little power. Checked codes and now have codes 15, 25, 27 and 32 showing. Sent the ECU back for warranty and they told me the codes we're "not active". They cleared the codes and are sending the ECU back to me (I don't have it back yet as of this post). Having all these codes at the same time leads me to believe they are using a shared 5V sensor power supply or similar. Anyone had this combination of issues before? Ideas? Solutions?

[csracing]

ECU is back and installed. Same codes present and now I have a code 74 back. Super fun. So frustrated.

[bpu699]

Originally Posted by Skip426

Welcome to iRV2.

Sorry your first post is about problems .
Here are a couple of pdfs on the operation of our Cat 3126Bs .
First one has the code list.
200 psi oil pressure cranking does sound low , I'd expect 800.

I should just bookmark all your posts, great info... thanks.

[gatorcq]

Just replace the IAP Sensor - First
Injection Actuation Pressure - $160