Author Topic: 1.5D bogging & power loss (Read 6031 times)

rabbicamino · « **on:** December 24, 2008, 09:15:54 pm »

Two months ago I converted my caddy from gas to diesel and have loved it more than ever. I don't think I'll ever go back to gas (especially to CIS injection), but one problem has been present since the swap was finished.
The truck runs great EXCEPT when I run high RPM or high throttle (~75%+). After the high fuel demand condition, when the throttle is closed and reopened, the engine bogs down almost to stalling (<500rpm) and the only way to prevent a stall is to hold the throttle to the floor for about 5 seconds until it slowly snaps out of it and runs normally again. I had an inline lift pump installed initially which I thought might be the culprit. I thought the IP might be trying to pull more fuel than the lift pump could provide during the high fuel demands, so I removed the lift pump today and the condition still exists. It is actually slightly worse than before. I am totally stumped, but I think there may just be a big air pocket in the IP or the lines. Please HELP!

rabbitman · « **Reply #1 on:** December 24, 2008, 11:34:34 pm »

So when your holding the pedal to the floor does the engine sound normal, of course there's the sputtering but does it knock extra bad?
Did you leave the gasser fuel pump on when you converted it?
Did the diesel engine run in before you installed it, or did it sit for a while?
Maybe try running some ATF in the fuel tank, you might have something stuck in there. Keep us posted

rabbicamino · « **Reply #2 on:** December 27, 2008, 10:05:03 am »

So, I thought the IP might have been overrunning the lift pump I put in there and starving it of fuel at higher rpms. I have heard that IPs move quite a bit of fuel one the rpms get up there so I pulled the truck up on a lift and pulled the pump out. Attempted to bleed the system quickly, probably didnt do a good job of it, and drove home. The problem is still there, only now MAGNIFIED somehow. :x :x . I thought I was done with drivability problems like this when I ditched CIS!!

At this point I decided that I could attempt an extremely thourough air bleeding. At the same time, I decided to also eliminate the possibility of clogged fuel filter and cracked IP feed line causing the issue. Replaced both items. I got out my trusty Mity-vac kit, and pulled air from the filter housing, return side of the IP, and the cross-over tubes at the injectors. I then started the truck and cracked each injector line. Upon revving the motor up off of idle, I could see a TON of air bubbles making their way into the IP through my new transparent IP feed line. A leak in the fuel line somewhere between the tank and the filter housing?

Yesterday I managed to sneak the truck back up on the rack at work again to find the leak. I started the truck and pinched the inlet fuel hose to the fuel filter housing and way more bubbles were visable in the IP feed line. If that happens, then the leak it probably at the filter housing. I installed new seal rings at all the connections on the housing. Still leaking. I then double hose clamped every hose interface from tank to filter (6 connections). Still leaking. Should I pressure test the line to see if I can make diesel come out? Replace the IP inlet banjo bolt with a regular bolt to plug it up and turn the lift pump on maybe?

rabbicamino · « **Reply #3 on:** December 27, 2008, 10:20:21 am »

Also, to answer rabbitman's questions:
1) The engine sounds normal, just surges as it pulls air in and pushes it out.
2)I did not use the CIS fuel pump. I purchased an inline fuel pump from NAPA that does 4-7psi and 36gph.
3)The 1.5D had been sitting for some years when I purchased it. It had been rebuilt, ran on a test stand, and then stored. The IP was about 1/4 full of really old looking diesel, but with the lift pump installed initially, the flow pushed the old crap out before I even cranked it over the first time. My first full take of fuel was B99, and yes I did use bio compatible fuel hose when I hooked everything up.
4) I havent ran any ATF through it, just B99, Diesel-Kleen, and Valvoline Diesel Cleaner. I have been running regular petro-diesel since that first tank of B99.

rabbicamino · « **Reply #4 on:** December 27, 2008, 09:38:47 pm »

bump for problem solving!

Rabbit TD · « **Reply #5 on:** December 27, 2008, 10:17:55 pm »

Do you have a good open return line setup as well? I'd just keep putting some atf or conditioner-cleaner in the tank and run it for a while and see if it improves if this is not your only vehicle. You will definately like your diesel and they cost next to nothing to run. If it is the IP thats the problem there are tons of them to be had for not too much. Make sure you get the dial indicator for the pump timing, you will be using it more than you think. You wouldn't believe how little movement of the pump it takes to change the reading and forget about scribe lines and all that, I don't know how I got by without one before. You'll get it figured out and when you start saving all that money on fuel you can spend it on everything else under the sun for these little things like the rest of us do.

Rabbit TD · « **Reply #6 on:** December 27, 2008, 10:58:40 pm »

Also did you blow air into the tank from the inlet and return line to the tank to check for any clogs. You did say it seemed worse after you removed your lift pump. It sounds like a restriction in the tank or something to me so far. I don't know if there is a difference in the tank between diesels and gas or not either as far as making a restriction or not. I have heard other people on here say though that bio diesel will loosen up gunk in a tank after a while and clogg your {what you think} is a new filter that you just put on and therefore rule it out as a possibility of the problem. It's always the simple ***, just finding it

rabbicamino · « **Reply #7 on:** December 29, 2008, 01:08:04 pm »

So I had some time yesterday for more diagnosis and it just made me more stumped. So last week I pinched the fuel filter feed line with the engine running and way more bubbles came into the IP feel line. So I'm thinking that air is getting into the fuel system from the fuel filter assembly somehow. Fastforward to yesterday, I get around to bypassing the filter all together to isolate the problem, and viola!!! The little diesel revvs up to redline, no bogging, etc..... So now I attempt to find the leak on the filter assembly. I make a banjo plug for the fuel outlet hose and attach my mityvac to the inlet. I pump the mityvac up to 20inches on vaccuum and it holds that for five minutes without a leak. Now I'm really stumped. I need a beer.

Rabbit TD · « **Reply #8 on:** December 29, 2008, 07:31:43 pm »

It sure sounds like the filter element to me if the vehicle runs fine with it bypassed. I bet when you went from gas to deisel the filter got a little plugged and it just took a while to show up. If your mighty-vac shows that the assembly holds vacum then you know that the assemly doesn't leak but how well will it flow? That's the main thing it has to do. I would put a new filter in and see if it makes a difference and if it does then you're good, and if it starts acting up little by little over a couple weeks then you know you have contaminated fuel. I do remember you saying it has been getting worse, filter probably getting more plugged the more you drive. Did you ever cut one of these things open with a hacksaw just to see how much *** is in one of these things, black goop, water, any thing else under the sun. Try it and see, I bet that's it. Good Luck :wink:

fatmobile · « **Reply #9 on:** December 30, 2008, 01:45:03 am »

Yep, I'm guessing there is a restriction in the fuel system.
No big surprise that when you pinch the line and cause a greater restriction; there are more air bubbles.
Use your lift pump to make sure fuel is pumping freely through the filter.

Make sure you have an "OUT" banjo bolt in the output of the injection pump,.. not the output to the injectors the output to the tank.

rabbicamino · « **Reply #10 on:** January 01, 2009, 02:04:08 pm »

It was the "out" banjo bolt causing the problem. Or rather, the lack of an out banjo bolt. I had two inlet banjo bolts on my IP, causing my IP to suck fuel to it's little heart's content without a restriction on the outlet side preventing residual pressure in the IP. Thanks all for your replies. I don't think I ever would have checked that and ripped my hair out instead. I work in a BMW parts department, so I went through the ETK and ordered the "out" banjo bolt for a 524td which also uses a VE pump. We'll see what happens. Also, I wonder how the 524td injectors compare to the 300td injectors for an upgrade. BMW used IDI diesels in europe through the late 90's in the 525tds E39 chassis, and also in the 318tds. Maybe an untapped resource since I dont have any problems getting euro parts like that into the US. :twisted:

rabbicamino · « **Reply #11 on:** January 10, 2009, 08:51:24 am »

I finally got the new "out" banjo bolt from the fatherland yesterday and I couldn't believe how small the outlet orifice is on that thing! I dont think I could stick the tip of my ballpoint pen into that hole. Put the bolt in and the bogging problem is now solved, but now when the rpms get up there the engine tries to run away on you! I adjusted the fuel bolt on the side of the IP and its not as bad, but the rpms hang if I rev it up before shifting. Pretty annoying. I have done the governor mod already, and the rpms hanging seem to have a linear relationship to how high the rpms are. Maybe they are related? When the rpms are low, like if you short shift it, the rpms drop right down very quickly. But there seems to be some crossover point in the upper rpms where it can't close off the fuel when you close the throttle. If it aint on thing its another :?

theman53 · « **Reply #12 on:** January 10, 2009, 12:14:24 pm »

while doing the governor mod what did you use and how far did you shim? I think your correct to start looking there. I only went 1/4" with washers and had no problems.

06SpiceRedTDI · « **Reply #13 on:** January 26, 2009, 01:21:18 pm »

The 1.5D had too small of an oil return from the head, this wasn't corrected until the 1.6D. The official VW fix for this that returns oil from the crankcase vent down to the block down by the Vacuum pump. what happens is the top of the head fills with oil and then it starts sucking it through the CCV and that is actually the oil that it is burning when it runs away.

Author Topic: 1.5D bogging & power loss (Read 6031 times)

06SpiceRedTDI