Cat 3126 B won't start ****HELP***

Hello and please help:

I have a 1999 Cat 3126B in my motor home which was running great until we got home from a long trip. After about 2 weeks of being idle, it would turn over but did not fire. I did not change any filters so they should be filled with fuel. No white smoke out of the exhaust when being turned over so I suspected the injector actuator solenoid valve was bad and replaced it. At the same time I changed the oil and replaced the filter so that is clean. I questioned if the manifold pre-heater was working and the relay was corroated so when I tried to loosen the connectors one broke so I put a new relay on which seams to be working (12 volts to it and resistance across the pre-heater.

It will start with some short blasts of either (I know, not recommended) and run fine after starting. When it was running after starting with either I filled it with fuel and brought it back home. Next day it would not start again. I’m wondering if I have a faulty fuel check valve and where it/they (supply and/or return) are? This engine has a small primer on the water separator filter but none on the engine and seconddary filter. Also where is the fuel transfer pump (near the HPOP)?

Any suggestions you may have would be greatly appreciated. My local (30 miles away) Cat dealer will not come down to run the codes and I hesitate using either to start it again.

Thanks
Bob

 

Thanks for your replies:

I ran the codes as Jas suggested and came up with 87 and 34 in that order. I think the 34 relates to the intake manifold air temp which I thought might be one of my problems and giving me trouble starting. Might also explain why it didn't explode when I used either the last time I was able to start it. I took off the air filter boot that connects to the manifold where the heater is and used a laser thermostat during the preheat cycle and nothing happened, stayed at 47 deg F outside and inside.

Going to pick up a new one shortly, one of my cheaper parts at $120.

I did try to preheat the chamber where the heater is with a heat gun but it just cranked and no pop.

Still thinking I might have more than one problem like a leaking check valve.

Your thoughts are appreciated.

Bob

 

PS: I have an HPOP that activates the injectors. Is that similar to a HEUI?

Side note; The RV was running flawless all year (a first) and even when we were in Cedar Rapids Iowa volunteering to rebuild homes after last years flood and temperatures were in the 30's. Got home and parked it in the driveway and that's where it died. Hay, it could have died in New Mexico so count my blessings.

 

PSS: I was wrong, code 34 is secondary speed sensor and I think I have to remove the air compressor to get at it.

Preheater was bad anyway so not a big deal but not looking forward to replacing the sensor in that tight area.

 

DDS Thanks:

It would appear that the sensors are directly under the fuel transfer pump from the picture Cat sent me. Just got the parts (sensors and O rings) but haven't crawled under the RV yet.

Do you loosen the old sensor bracket bolt and then bend the fingers of the bracket to get the old sensor out, install the new sensor then bend the fingers back down? I see how they will pop out of the new bracket and they have different numbers on each sensor so I'm sure they have to go in as they are on the bracket. You make is sound easy, how are my knuckles going to look when I'm done?

Thanks again, hope that's the problem.
Bob