TDC Sensor

JR · Post by JR » Tue Feb 05, 2002 11:24 pm

I have a 79 fi bus im trying to get running. I have everything hooked up right but I cant find where to hook the tdc sensor up to? There seems to be no connection for it. Dosent it need it for the fuel inj.Also would not having it hooked up , make the fuel pump not work? Any comment would be greatly appriciated!

ray greenwood · Post by **ray greenwood** » Wed Feb 06, 2002 10:42 am

Check the right hand side of the bell housing flange behind the throttle body. There should be a drilling there. Ray

JR · Post by JR » Wed Feb 06, 2002 4:48 pm

Hey guys thanks for the imput,but my problem is the tdc sensor is in and I am looking at the other end {the three prong plug} of it. I got another manual today,havnt looked at it yet . Man I feel like an idiot! I know it has to plug into the harness somewhere , to tell the feul inj. and the computer where tdc is ,right? Well, back to the books ! Thanks for your time, JR.

germansupplyscott · Post by **germansupplyscott** » Wed Feb 06, 2002 8:48 pm

JR,

i don't have one on my bus, also a 1979, so i can't speak from recent experience BUT...

the TDC sensor is for tuning the engine, it should not be required for the engine to run at all. and it has absolutely no connection to the fuel pump. the TDC is, i believe, only there for a mechanic to diagnose and tune the motor, it has no "feedback" to any other device on the motor, not FI, ignition etc. the L-jetronic system has no means to interpret the data from a TDC sensor, correct me RAY if i am wrong about this.

so, if you are thinking the TDC is at the root of some problem, then be relieved that it probably lies elsewhere.

scott lyons

JR · Post by JR » Wed Feb 06, 2002 9:55 pm

Hey yall, after doing some reading and checking, I came to that conclusion also. I think the fuel pump is the problem.It gets power while crankng the motor but there is no pressure in the line. Does the computer get its signal from the - side of the coil to know when to fire the injectors? If so how does it know which pair " I Think" to fire in sequence with the right cylinder? Hope these questions dont seem to stupid! thanks for all the imput!!! JR

rich2481 · Post by **rich2481** » Wed Feb 06, 2002 11:36 pm

I do not have one on my 1980 either.

rich2481 · Post by **rich2481** » Thu Feb 07, 2002 7:44 am

You should be able to hear the fuel pump when cranking, might be a two person job, but you are correct the book says that the fuel pump will only run when engine is cranking, they are easy to test though, check fuses too sometimes on the older cars those " hat " fuses get oxydation on them and they look good but do not make contact,

I wiggle them every so often back and forth and sometimes take emery cloth to buff them back to life.

germansupplyscott · Post by **germansupplyscott** » Thu Feb 07, 2002 8:33 am

JR,

there is an easy way to turn on the pump when checking the pump operation. remove the air filter box from the air flow meter. to do this it may be necessary to disconnect the afm from the the intake air elbow, then remove the entire afm and air filter box as a unit from the van. this sounds complicated, but it is not. there are four screws attaching the afm to air filter box. remove these and then install the afm back onto the van (without the air box) and hook it up. with the key in the run position, put your finger into the open end of the afm (where the filetr box was connected) and gently push the air flap open. this should open the fuel pump contacts on the relay and start the pump. the advantage to this method is that the motor does not need to be running or cranking, so there is no other noise to distract from the test. you can now test the various aspects of the pump operation while you are in the engine compartment.

since the pump is making noise, first suspect the fuel filter and replace, using only the correct bosch filter. replace all the fuel lines while you are at it, and use only metric sizes, the imperial hoses will not fit correctly. vw dealer or benz dealer have the right hose, and you don't need much so don't be afraid of the cost. you need 7mm hose for most of it and a short piece of 12mm for the filter to pump inlet. use only the correct non-perforated hose clamps, not the hardware store kind with holes in the band - they destroy the hose and will cause an engine fire. i am belaboring the fuel line issues for a good reason - if you don't listen to this advice, you may have a fire, ask me how i know... - fuel line failure caused fires and are very common in vans, and if you are dealing with you fuel lines, the ONLY way to do it is to replace all the lines with the correct german hose and clamps, anything less is asking for a fire. be careful when working with fuel line, have an extiguisher on hand at all times, i am being silly i know, but this is all very critical. you want to keep yourself and your van safe.

scott lyons

[This message has been edited by punkinfair (edited 02-07-2002).]

ray greenwood · Post by **ray greenwood** » Thu Feb 07, 2002 3:38 pm

Bravo...good info Scott. Ray

JR · Post by JR » Thu Feb 07, 2002 11:10 pm

Hey everybody, thanks for all the excellent input,very good safety tip on the fuel pump lines and clamps.I did change the filter earlier, but like I thuoght the pump was bad,picked up another used { but garenteed} pump today. Put it in, primimed the engine, + fuel pressure, oil light went out ,hook back up the - dist, wire, " BAMB " starts without missing a beat,from a big box and bus full of parts to purring in front of you ,what a good day to be alive! Thanks again everybody for your imput, I'm already starting to twitch wondering what the next project will be ,se yall later! JR