Clark Posted August 29, 2009 Share Posted August 29, 2009 Ive got a '95 school bus with a Bosch pump 466. It loses fuel pressure under a load. It will run all day long idling or high idling, but as soon as it goes under a load, it will slowly lose pressure. It will not restart unless you hand prime the system. It also smokes white heavily when it starts losing pressure. I cracked the bleeder on the injection pump, and it had a ton of air in the fuel. I inspected the suction line from the lift pump to the tank, and found it had several rubbed spots (nothing looked rubbed through, but a few spots were close). I replaced the line, and it still had air in it. So I put a sight glass on the line right as it came off the pickup tube, and theres no air in it. I pulled the fitting that goes from the suction line to the lift pump (2 piece with banjo fitting to pump) and inspected it. I pulled it apart, resealed it, and put new copper washers on the banjo fitting. Still has air. I replaced the lift pump. Still has air. My foreman made 2 calls to a local pump shop and they said theres ABSOLUTELY no way the pump could be doing anything to aerate the fuel. I also took both pressure lines (lift pump to filter module & filter module to injection pump), and blew air through them to see if maybe they had blockages, as well as bypassed the filter module for a short time to see if it had a blockage (already had brand new filter on it). Any ideas? Quote Link to comment Share on other sites More sharing options...
International Tech Posted August 29, 2009 Share Posted August 29, 2009 Does this pump have the aneroid valve on the rear of the pump? Does it have a secondary filter base? Sounds like a filter base issue. Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted August 29, 2009 Share Posted August 29, 2009 There's a huge pattern failure with the suction tube in the tank coming loose from the fitting from a cracked solder joint. Slide the fuel tank out enough to access the dip tube, remove it, check for a cracked joint, and check for debris that could occasionally be blocking the tube or elbow fitting at the top. I've seen this problem numerous times, and I'm betting the fitting is cracked or the tube has an intermittent obstruction. If the fitting is not cracked, remove the tank and clean it manually- have two guys slosh the tank back and forth holding it between them, and then invert it into a clean white 5 gallon bucket to drain. Put another 2-3 gallons of fuel in it, agitate it manually vigorously again, and invert it again. Keep this up until the fuel comes clear from the tank. You might be surprised at the crap that comes out of the tank. If the dip tube obstructs occasionally, it will give the exact complaint you have. Good Luck! Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted August 29, 2009 Share Posted August 29, 2009 PS I had one with the filter header fitting clogged with debris, too. Unbolt the filter header and disassemble it in the solvent tank, and blow out the fittings. I think there's only two bolts holding it to the block. Wood chips seem to be a common substance that clogs the intake system, especially if the fuel gauge doesn't work, as the driver uses a stick to check the fuel level. Does he get a clean broomstick from the shop? No, why bother. This rotten tree branch laying right here will do fine.... Other things found in tanks- silver foils from fuel additive bottle seals, plastic wrapper from a sandwich, (that was invisible sitting in diesel fuel) and a complete size XL sweatshirt. (good story behind that one....) Sidebar: This is a one year pump and engine that got caught in the EPA emissions crossfire. Does it have the infamous cold run complaint with smoke and lack of power? There's a TSI letter on advancing the timing a couple of degrees that does WONDERS for how this engine runs. There's an aneroid update for the pump, too, that should be done by a pump shop if it doesn't run just perfect. I love this engine and know it WELL....... Good Luck! Quote Link to comment Share on other sites More sharing options...
LARRY BRUDZYNSKI Posted August 31, 2009 Share Posted August 31, 2009 My foreman made 2 calls to a local pump shop and they said theres ABSOLUTELY no way the pump could be doing anything to aerate the fuel. Clark sounds like you have covered everything except the most common problems,( the local pump shop should have recommended the check valve ), that we see around here. Replace your check valve, it's on the pump between the pump and head. We have had quite a few shops replace pumps for bad check valves. Quote Link to comment Share on other sites More sharing options...
Clark Posted August 31, 2009 Author Share Posted August 31, 2009 There's a huge pattern failure with the suction tube in the tank coming loose from the fitting from a cracked solder joint. Slide the fuel tank out enough to access the dip tube, remove it, check for a cracked joint, and check for debris that could occasionally be blocking the tube or elbow fitting at the top. I've seen this problem numerous times, and I'm betting the fitting is cracked or the tube has an intermittent obstruction. If the fitting is not cracked, remove the tank and clean it manually- have two guys slosh the tank back and forth holding it between them, and then invert it into a clean white 5 gallon bucket to drain. Put another 2-3 gallons of fuel in it, agitate it manually vigorously again, and invert it again. Keep this up until the fuel comes clear from the tank. You might be surprised at the crap that comes out of the tank. If the dip tube obstructs occasionally, it will give the exact complaint you have. Good Luck! I thought that because there was no air in the fuel after it that is an indication that the suction tube is not cracked? We have a tank cleaning machine. Ive never used it personally, but seen it used several times for cleaning rusted out tanks. Would that be as good as cleaning it manually? Quote Link to comment Share on other sites More sharing options...
Clark Posted August 31, 2009 Author Share Posted August 31, 2009 PS I had one with the filter header fitting clogged with debris, too. Unbolt the filter header and disassemble it in the solvent tank, and blow out the fittings. I think there's only two bolts holding it to the block. Wood chips seem to be a common substance that clogs the intake system, especially if the fuel gauge doesn't work, as the driver uses a stick to check the fuel level. Does he get a clean broomstick from the shop? No, why bother. This rotten tree branch laying right here will do fine.... Other things found in tanks- silver foils from fuel additive bottle seals, plastic wrapper from a sandwich, (that was invisible sitting in diesel fuel) and a complete size XL sweatshirt. (good story behind that one....) Sidebar: This is a one year pump and engine that got caught in the EPA emissions crossfire. Does it have the infamous cold run complaint with smoke and lack of power? There's a TSI letter on advancing the timing a couple of degrees that does WONDERS for how this engine runs. There's an aneroid update for the pump, too, that should be done by a pump shop if it doesn't run just perfect. I love this engine and know it WELL....... Good Luck! I actually bypassed the filter completely and ran it shortly and it still had the concern. They were not complaining about cold starting. The timing is currently at 14 degrees BTDC, spec is 12 degrees. As far as the aneroid update, Im not sure. Is there anyway to tell by looking at it if its been done or not. The engine has had its injection pump changed. Quote Link to comment Share on other sites More sharing options...
Clark Posted August 31, 2009 Author Share Posted August 31, 2009 Originally Posted By: Clark My foreman made 2 calls to a local pump shop and they said theres ABSOLUTELY no way the pump could be doing anything to aerate the fuel. Clark sounds like you have covered everything except the most common problems,( the local pump shop should have recommended the check valve ), that we see around here. Replace your check valve, it's on the pump between the pump and head. We have had quite a few shops replace pumps for bad check valves. By check valve do you mean the pressure regulator on the return line or is it in the pump itself? Ive already had a test regulator on it and it didnt fix it (forgot to mention it). Its also got a new set of nozzles in it (forgot to mention). Quote Link to comment Share on other sites More sharing options...
LARRY BRUDZYNSKI Posted August 31, 2009 Share Posted August 31, 2009 It goes in the pump between the head and pump. It goes directly into the pump and the return line banjo goes into it. The Bosch number on it is 2-417-413-076 I have it on the shelf or you may try your local pump shop. Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted August 31, 2009 Share Posted August 31, 2009 Larry's talking about the "overflow valve", or return valve on the return line at the rear of the Bosch pump. Pull it out and inspect it. I think it will cause more trouble on a no-start, loses prime problem, but you never know. On the inlet side, there should be a check ball in the filter header like this: The pics are from a DTE but yours should look very similar. Check the PN with the parts department to make sure it's correct for a DT. Make sure the ball is yellow and not shredded. If it's shredded, find the chunkies! If it's a black ball, replace it. They're only about $6. Good Luck! Quote Link to comment Share on other sites More sharing options...
Clark Posted September 1, 2009 Author Share Posted September 1, 2009 Larry's talking about the "overflow valve", or return valve on the return line at the rear of the Bosch pump. Pull it out and inspect it. I think it will cause more trouble on a no-start, loses prime problem, but you never know. On the inlet side, there should be a check ball in the filter header like this: The pics are from a DTE but yours should look very similar. Check the PN with the parts department to make sure it's correct for a DT. Make sure the ball is yellow and not shredded. If it's shredded, find the chunkies! If it's a black ball, replace it. They're only about $6. Good Luck! The overflow valve, I think Im still confused. It looks similar the the valve on the back of the 466E oil manifolds, correct? If so, like I said, I already swapped it out. Does anyone have a picture maybe? As far as the check ball on the inlet side. The filter module and hand primer on this engine is not similar to that. It mounts the filter upside down and uses a smaller fuel filter. It has a hand primer on the left side that you unscrew and pump after turning a knob. Quote Link to comment Share on other sites More sharing options...
LARRY BRUDZYNSKI Posted September 1, 2009 Share Posted September 1, 2009 No, I'm not talking about the check ball on the inlet side of fuel. By what you have checked and replaced it's not coming from the inlet side. Clark are you familiar with the Bosch P series pumps? This is a similar pump in regards to the fuel return. Instead of the banjo bolt having the check valve in it, this actually has a dedicated check valve that the banjo bolt goes into. P/M me your email and I will send you a pic of it. I have the fitting sitting on my counter at work. Another question??? How many miles and how does the throttle shaft look??? I have seen the throttle shafts wear out and start to leak, could be a source to suck air in from. Quote Link to comment Share on other sites More sharing options...
Clark Posted September 1, 2009 Author Share Posted September 1, 2009 No, I'm not talking about the check ball on the inlet side of fuel. By what you have checked and replaced it's not coming from the inlet side. Clark are you familiar with the Bosch P series pumps? This is a similar pump in regards to the fuel return. Instead of the banjo bolt having the check valve in it, this actually has a dedicated check valve that the banjo bolt goes into. P/M me your email and I will send you a pic of it. I have the fitting sitting on my counter at work. Another question??? How many miles and how does the throttle shaft look??? I have seen the throttle shafts wear out and start to leak, could be a source to suck air in from. PM sent. For the record, I have almost no experience with ANY injection pump. I cant recall the miles right now and I havent inspect the throttle shaft. Ill get back to you about it when im back at work tomorrow. Quote Link to comment Share on other sites More sharing options...
LARRY BRUDZYNSKI Posted September 1, 2009 Share Posted September 1, 2009 Check the shaft for any movement up,down,forward or back, or leakage. I'll send the pics in the A.M. Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted September 1, 2009 Share Posted September 1, 2009 The overflow valve, I think Im still confused. It looks similar the the valve on the back of the 466E oil manifolds, correct? Yes, very similar. If so, like I said, I already swapped it out. Does anyone have a picture maybe? Can you believe, I can't find a pic? As far as the check ball on the inlet side. The filter module and hand primer on this engine is not similar to that. It mounts the filter upside down and uses a smaller fuel filter. It has a hand primer on the left side that you unscrew and pump after turning a knob. Is this an old rental truck? It sounds like it from the FF you describe. Quote Link to comment Share on other sites More sharing options...
blown99 Posted September 2, 2009 Share Posted September 2, 2009 The upside down fuel filter was a Ryder special. Kind of a PITA. Run a fuel line from the suction of the fuel transfer pump and over into a bucket of fuel - how does it run. I have also applied regulated shop air to either the fuel tank and or at the pick up tube hose and pressurize the system. Then spray the system with soapy water to detect your leaks. Put a vaccumme gauge at he hose that connects to the pick up tube and crank the engine- what does it pull for vaccume? Does this truck have two fuel tanks? Crossover line under the tank or does it have the siphon system? Quote Link to comment Share on other sites More sharing options...
Clark Posted September 2, 2009 Author Share Posted September 2, 2009 Check the shaft for any movement up,down,forward or back, or leakage. I'll send the pics in the A.M. Got the pic, thanks. Like I said, I already swapped that out and it did not make a change. Today I got put on another job so I was only able to work on it for a bit, but my foreman just suggested that I verify the fuel level once more, just to be safe (fuel gauge inop). Just looking at it, it seemed to have enough fuel in it, but I decided to put a few gallons in it anyway. Test drove it afterward, and the bus had no issues. Now, either I made the biggest rookie F%&* up yet and just ran it too low diagnosing another issue this thing had and the fuel sloshing around in the tank was enough to kill it while driving, or theres something in the tank and the extra fuel in the tank kept it out of the pickup tube. At least thats all I could think of. Quote Link to comment Share on other sites More sharing options...
Clark Posted September 2, 2009 Author Share Posted September 2, 2009 Originally Posted By: Clark The overflow valve, I think Im still confused. It looks similar the the valve on the back of the 466E oil manifolds, correct? Yes, very similar. If so, like I said, I already swapped it out. Does anyone have a picture maybe? Can you believe, I can't find a pic? As far as the check ball on the inlet side. The filter module and hand primer on this engine is not similar to that. It mounts the filter upside down and uses a smaller fuel filter. It has a hand primer on the left side that you unscrew and pump after turning a knob. Is this an old rental truck? It sounds like it from the FF you describe. School bus. Quote Link to comment Share on other sites More sharing options...
Clark Posted September 2, 2009 Author Share Posted September 2, 2009 The upside down fuel filter was a Ryder special. Kind of a PITA. Run a fuel line from the suction of the fuel transfer pump and over into a bucket of fuel - how does it run. I have also applied regulated shop air to either the fuel tank and or at the pick up tube hose and pressurize the system. Then spray the system with soapy water to detect your leaks. Put a vaccumme gauge at he hose that connects to the pick up tube and crank the engine- what does it pull for vaccume? Does this truck have two fuel tanks? Crossover line under the tank or does it have the siphon system? Already did all that, new line to the tank put in, etc... Vacuum was good. Single tank. Quote Link to comment Share on other sites More sharing options...
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