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vwbugman
vwbugman, VW Technician
Category: VW
Satisfied Customers: 820
Experience:  35 years experience on VW air cooled and water cooled repair and restoration
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1978 VW Beetle: dies..Replaced fuel pump..Blew out fuel lines as it

Customer Question

1978 VW Beetle FI starts and dies at times otherwise is a no start. Replaced fuel pump, filter and tank as it had been sitting and junk. Blew out fuel lines as it was full of junk. Good spark and fuel pressure jumps to over 90 psi if return is pinched off. Starts if starting fluid is sprayed into intake. with fuel injector removed there is no spray when cranking. Replaced injector with no change. Test light across injector harness flashes faintly when cranking. Help!
Submitted: 6 years ago.
Category: VW
Expert:  vwbugman replied 6 years ago.

If your fuel system was full of trash, you are in trouble with the system. It is very hard to get it clean. All lines must be flushed, hoses replaced,etc. If you are getting a pulsation at the injectors, the injectors must be plugged up. It will continue to get cantamination when the fuel pump runs. Is the fuel pump running when cranking?

 

The most economical thing to do is a carborator conversion. If you want more information on this I can give it to you.

Customer: replied 6 years ago.
But I have replaced injectors and no spray anywhere when cranking and there is fuel pressure of near 50 psi when cranking. I'm taking fuel pressure at rail right before injector. I've clean and/or replaced all fuel lines.
Expert:  vwbugman replied 6 years ago.

You need to see what the voltage is at the injector. There is a voltage reducer pack on the right side on the side of the engine compartment. This reduces the voltage. It is small silver box with white wires and a plug in. This could be faulty. There are many things on the fuel injection system that can be faulty. That is why most people will do a change over to carboration. There are very few people who can diagnose the issues without some sort of experience because the system is so old. I could figure it out but I also have an ample supply of parts to try on it. It can get expensive as you are finding out to repair this fuel injection and frustrating. You need a good OEM VW manual that covers the fuel injection so you can troubleshoot. There is usually no simple solution.

 

Here's a list of things that could cause it.

 

  • Improper fuel pressure
  • Faulty ECU (computer)
  • Bad injectors
  • Stopped up injectors
  • Faulty temp sensor ( located on the left head)
  • Faulty air flow box
  • Short in wiring
  • Bad grounds
  • Fuel pump relay

 

vwbugman, VW Technician
Category: VW
Satisfied Customers: 820
Experience: 35 years experience on VW air cooled and water cooled repair and restoration
vwbugman and 4 other VW Specialists are ready to help you
Customer: replied 5 years ago.
What should the voltage at the injector be??
Expert:  vwbugman replied 5 years ago.

I am at home now but if you can wait till morning, I will check my manual and see. What voltage do you have?

 

rick

Customer: replied 5 years ago.
I wasn't sure how it was to be checked. With all injectors unplugged there is battery voltage. With 3 plugged in and checking the fourth one unplugged it is aprrox. one volt.
Expert:  vwbugman replied 5 years ago.
What do they do if you take direct 12v from the coil to them with a jumper wire?
Customer: replied 5 years ago.
Is there any way I can call you or you call me and talk about this problem?
Expert:  vwbugman replied 5 years ago.

I have the book in front of me now. There should be a constant supply of current to the injectors. That supply comes from terminal 88b on the double relay. The control unit supplies a negative ground to all 4 injectors simultaneously. The negative ground breaks with each opening and closing of the points. THe series resistant block keeps a constant voltage. It does not give me the voltage specs but I don't think 1 volt is enough. You should have 12 volts to the restance block Do you have access to VW official repair manual? It gives all the testing procedures. Have you check the temp sensor on the cylinder head. At 68' it should read 2500 ohms. I think you either have a faulty resistance block or temp sensor. I am not allowed to give out phone numbers or email addresses on this site or I will be booted off as an expert. I'll try to figure something out.

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vwbugman
vwbugman
VW Mechanic
820 Satisfied Customers
35 years experience on VW air cooled and water cooled repair and restoration