jcb with perkins engine constant air problem in fuel.

I am working on a JCB backhoe with a perkins 4 cyl has new supply pump and rebuilt injector pump. Pump was rebuilt due to dying problems and was told the fuel leaking from a weep hole was a indicator it had failed. Got pump back on and timed finally started after much cranking and bleeding. Ran fine that night but would not start the next morning unless primed and a shot of either. Fast forward to last night found air entrapment in the fuel filter, and pulled the return line off and it had a fair amount of pressure. I think its froze because I cant blow, pull vacuum or compress the line to clear it. I primed the supply pump and had to block the return line with my finger it fired right off. I have to then let the return line flow freely into a bucket for it to stay running. While its running the fuel will start out a good steady stream and slowly turn to a frothy mix of fuel and air. Now if I plug the return line back off it dies after about a min and will not restart unless primed and whole process repeated. I pulled vacuum on the fuel lines (like checking a short started at the tank and ended at the fuel pump) found what seems like air coming from the sediment bowl but not sure. This fuel system is like nothing Iv'e never seen before any suggestions?

also if anyone could tell me what the small line coming from the fuel filter housing to the intake manifold is that would be great. it comes off a T on top along with the return line from the IP and the return to the tank.

Need more info, what is the pump model/dispatch number? Most Perkins in MF applications have a constant bleed orifice fitting on top of a filter base that usually is hooked into the injector top leak off line, then goes back to the tank. The bleed fitting is there to remove any trapped air from the filter base so NO air gets to the injection pump. When the orifice gets plugged it WILL cause trouble when air gets into the injection pump. Not sure if JCB has the same fuel system setup. Also, if NAPA/WIX fuel filters are used MAKE SURE the filter top outer groove DOES NOT have an O ring in it, that's the filter fuel inlet. It's a common mistake on that type filter that fellows will put an O ring in that groove, severely restricting or shutting fuel flow off completely.

Small fuel line to the intake manifold is probably feed line to the Thermostart cold start heater.

ok I will have the guy send me a pic of the injector pump name plate. as for the constant bleed fitting are you referring to the what appears to be a banjo bolt in the top of the fitting where the tank return line comes from. also I was mistaken that same fitting it is a 4 way fitting it has the excess fuel from the injectors coming into the back side.

this hoe uses a spin on type fuel/water separator filter. I don't remember the number right off hand but it is a wix filter. it uses the basic spin on mating gasket.

I know this will happen on a turboed engine, but I don't know if yours is turbed That said, the small line going to the intake is a feed line for a cold/flame start element. As the element heats up it opens a valve that allows a fuel to hit the heated coil and atomize to create a flame to heat the intake air.

Here's where I've seen problems. The element has a valve in it. If it's a turboed engine, as the turbo builds boost pressure it can push air into the fuel system if the valve in the heating element goes bad and isn't seating properly.

I nearly pulled my hair out on one years ago. I had the pump rebuilt, changed the transfer pump, changed all the soft lines, and anything else I could think of. I finally pulled the line to the element to get an actual fuel pressure reading (knew it was getting fuel so I hadn't worried about that previously as it's usually not an issue)...

Anyway, when I pulled the line and hooked it to a guage instead of the element, the engine began to run like it should. I hooked the line back up and the problem came back.

I changed the element and never had another problem. During the course of the troubleshooting I had talked to everyone I knew, who knew anything,and none had ever experienced this problem. When I figured it out I called one of the guys back and when I told him what I found the phone got silent. He finally remembered running into the same problem about 15 years before....

Good luck, and I hope this helps.

thanks for that I will not be near the backhoe for a few days but I will look into it. I'm still waiting on the guy to send me the model and SN for the pump.

That could very well be the problem. The CAV/LUCAS/Delphi Thermostart listing shows different part numbers for use on turbocharged applications. Maybe his is leaking back. Service book also stresses that there must be fuel at the inlet at all times, quickest way to burn one out is lack of fuel, then the coils inside overheat and fail, so when they cool again the internal valve can't seal as it should.

I forgot there to day it's not turbo but I will look at it.

You need to be more precise with the model of the JCB you have,all the JCB's with the Perkins 4.236 or 4.236T has bog standard fuel injection system that is common with any MF tractor that uses Perkins engines,the machines can differ from the older type that had the fuel tank as an integral part of the frame or has it the newer style with a separate tank that doubles as a step to get into the cab,the older type had a CAV rotary injector pump,the very early ones had a pull stop,then electric stop,older ones had to be bled then the newer ones were self bleed,CAV sold out to Lucas and Lucas to Delphi,so as you see there are lots of models,I am in the UK and have worked on them all,I cannot remember any weep holes on any injector pump that would indicate it needed changing and as it did not cure your problem you were duped into buying a pump,the first thing that I would have looked at is the fuel leaving the tank under gravity,if not a good flow check the tank is vented,if that's ok you will have to undo the fuel line from the nipple on the bottom left of the fuel tank sitting in the seat,secure the loader raised and access the fuel line to the tank from the engine bay,after the line is off you may poke a wire up the hole to clear it,and drain the tank,there is a bigger adapter that screws out so you can flush the tank out,if you have a good flow from the tank check the line to the feed pump is not kinked or pinched under something,take the top cover from the feed pump to see the fuel is coming to that point,after that the fuel is under pressure through the s/bowl and filter,there will be nothing wrong with any of the leak off plumbing,the small pipe you mentioned is for the heater plug,the plug should not let fuel pass through till the key is held in the heat position,when the element glows in the plug the ball valve is pushed off it's seat and the fuel passes through and catches fire to aid starting,check the flow from the tank and see how it goes.
AJ

it s a jcb 214e series 3 with Perkins 4cyl. I thinks it's the sediment bowl due to air pulled in with vacuum pump at the sediment bowl but good flow from tank.

If yours has the sediment bowl inside the chassis by the starter motor the plumbing should be the feed from the tank in with the out going to the feed pump,at that point the fuel should be under gravity as the tank is higher,if its pulling air that means that something is restricting the fuel flow,blow out the lines,you say you fitted a new feed pump are you sure that the actuator arm is the is on top of the camshaft,from the feed pump on the fuel is under pressure and should there be any bad joints you would have an external leak,if you suspect the sediment bowl you can bypass it for a test.good luck.
AJ

Not sure what model you are working with, I had a similar issue with my 1400b, only to find there is another fuel filter, mounted under the cab, one of the fittings to that filter housing was sucking air....

thanks for that info. I have a new sediment bowl Coming. This backhoe however,the tank is about level maybe a little lower than the sediment bowl but is in the position that you specified. I pulled vacuum on all the lines and the only place air was coming from the sediment bowl. Now the sediment bowl is a homemade piece of pipe that was welded up and made some washers and gaskets to make it fit. So I am sure that is where the problem is at. I did not put the fuel pump on so it is possible that could be a cause but it starts and runs fine as long as I take the fuel to tank return line off and let it vent the air out. I hook it back up and it dies within 1 min. Checked the fuel filter and it's full of air and little fuel. Reprime and bleed air it starts right back up. By the way it's a job 214e series 3 mid 90s do not have the serial number.

I hope this resolves your problem. They can be frustrating.