1973 Porsche 914 1.7 D-Jet

[crodog1]

I have no power to injectors on one side of my engine. #1 and #2. I have checked the grounds and they are good. The engine runs but 1 & 2 are not working. Have spark but no power to the injectors. Where does the power come from?

[raygreenwood]

No. You still most likely have a ground problem. Let me explain.


Ok bear with me because i am going to walk through a few things.

The system has inputs and outputs. On the input side.....the cylinder head temp sensor, intake air temp sensor, throttle valve switch, manifold pressure sensor and most importantly for your issue.....fuel injection trigger points.

These points are in the bottom of the distributor and have a three wire plug.

So all the other sensors aside for the moment.....the trigger points do several things:

1. They give the ECU an rpm signal

2. They give an injection window of time based in degrees. Each pair of injectors has 180° of open time available on the distributor drive. This does not set the pulsewidth of the injector.....it simply gives an allowable window in degrees within which each pair of injectors is allowed to fire.

At low load and rpm.....the pulsewidth (the time in milliseconds the injector is spraying) calculated by the ECU.....may not even span the entire 180° allowable window of time/degrees. At high rpm and load.....the pulsewidth can expand to fit the whole 180° time window.

3. On some D-jet....I am not sure about all.....each injector channel.....and there are two channels.....one for cylinders 1 and 3 and one for cylinders 2 and 4......is a collapsing circuit. If one circuit does not fire or collapse....the other cannot arm itself.

Normally......if a pair of injectors is not firing......the first suspect part is the trigger points. The rubbing block on one trigger may be worn down or one set of trigger points may be dirty or rusted......or....and this is most common.....one of the pins in the three prong plug may be corroded or loose inside the plug.

Bear in mind......these triggers just say when and within what window of time a pair of injectors can fire. They are just switches.....and give an input signal to the ECU.

The ECU then decides exactly how long the pulse will be.....and has output wires.....seperate positive power wires to each injector.....and...even though each injector has a separate power/signal wire from the ECU....AND each injector has its own ground wire going to the emgine block......the ground wires are PAIRED together where the connect to the engine block.

So......these are your choices:

1. if the problem were one side of the trigger points....or the plug at the trigger points or the wires from the trigger points plug to the ECU......of which there are only two......you would either not run at all (all four injectors not firing)......or one pair would not fire.....and those pairs would either be 1 and 3 not firing or 2 and 4 not firimg because that is how they are paired.

You would NEVER have both injectors on one side of the engine not firing because of something on the input side.

So.....its not your trigger points or the plug or the wires between the triggers and ECU.......because.....one injector on each channel IS firing...so both injector channels are getting input from the trigger points.

2. You could have broken output wires between the ECU and the injectors on the 3 and 4 side. Injector # 4 uses wird #4 and injector #3 uses wire #6 coming from the ECU plug.

3. Or the fork shaped pins in the ECU plug for #4 and #6 wires could be dirty, corroded or loose.

4. Or...and this is very, very common.....the female pins inside the plugs for injectors # 1 and #2...are loose and not making contact. The D-jet female connectors suck. Just like their larger cousins inside of your fuse panel......over time....with a few cycles of plugging and unplugging....not to mention heat expansion and vibration.....the little rolled sides of the connectors get loose and do not make contact with the male pins...even though the plastic plug body feels tight in the injector.

You need to take a pin out tool or jewelers screwdriver and delease the tab and pull the female connector out of the plug...and with small pliers....gently squeeze the sides of the female connectors to tighten the fit on the male pin.

Or......the female or male pins may have corrosion on them.

5. Or.....and this is the most common problem out of all of them......the female connectors of the ground wires in the injector plugs may have the same issues as the power wires described above........or.......since both injectors have seperate ground wires....it is possible that both may be broken between the injectors and the engine case.......

Or.....and this is most common.....since the ground wires from injectors 1 and two are paired together at a single female terminal at the engine case.....the crimp at that female connector is either poor or corroded.

So.....the question is....how are you checking the grounds? Ray

[crodog1]

Wow, that is all great information. Thx for taking the time to type that all out.

The way I checked the ground is with an Ohms meter. I unplugged the injector and tested the lead. One side showed the ground was complete because the meter went to 0 when I touched it to ground. Is this not a good test? The injectors on 3 & 4 have 12V on them when the key is on but 1 & 2 don't show anything. I will try removing the ends from the plastic plugs and tighten up the ends. Where would I find the grounds for the injectors?

[raygreenwood]

[crodog1]

Well I took out the injectors, removed the black plastic collar and could not push in the pins that were sticking out of the injector end. I pushed pretty hard but they did not move. Is it just best to replace them with new? I assume they are bad, right?

[raygreenwood]

[crodog1]

Thx for your help. I think they are both toast. I can not get them to move at all. I pushed on them pretty hard and the will not move. I also had problems with the fuel pressure regulator too. I had to replace it too. It was rusted so badly it would not allow the fuel to even come thru. I am sure that is why the injectors are bad I think. I will have to put this on the back burner until next wk. end. But with your help I think the problem is solved.

thx again.

[raygreenwood]

[crodog1]

Yes I had to remove the tank and have it cleaned. The car sat for about 6 years. I am trying to bring it back to life.

[raygreenwood]

[crodog1]

OH I had to replace the fuel pump too. It would not run at all. One thing I noticed is the new injectors don't have a pin sticking out of them like the old ones do. Is that going to be OK?

[raygreenwood]

[crodog1]

I have not purchased anything yet because they really look different. This is what they have for info: Fuel Injector Standard FJ114 fits 70-73 Porsche 914 1.7L $60 each

They dont have a pintle I tried to post a pix but it would not allow me.

I have only looked on the bay for them. I have this feeling they are not the correct one's. I did see one listed that looked like the same thing but it was $150 for one plus $8 shipping.

I also found these; GP Sorensen Fuel Injector from Auto Zone. Fuel Injector Type: MPFI (Port or Multi-Point Fuel Injection)
Injector Plug Type: For D-Jetronic

What do I do?

[raygreenwood]

Well.....the FJ114 is made by Standard Motor products.

Found an Amazon review that was positive. As long as the flow rate and resistance is normal.....and it fits.....its should work.

Really if what I remember about these is correct... it does have a pintle below the nozzle. Dont quote me on that yet.

https://www.amazon.com/Standard-Motor-Products-FJ114-Injector/product-reviews/B000C7Y4LM

I am finding them for as low as $49.....Rockauto has them for this price.

Lots of people selling them....everyone from Autohouse Az etc.

Let us know how they work please! And....when you get them could you please measure resistance and post it?

Thank you! Ray

EDIT......
This is a super fine site for buying and cross matching injectors.
Motorman lists the FJ114 as a Bosch replacment/crossmatch.

http://www.fuelinjector.citymaker.com/catalog/item/7638068/9492478.htm

Here is the main site

http://www.fuelinjector.citymaker.com/Fuel_Injector_Flow_Rates.html

[crodog1]

well I am beginning to understand why so many people get the injection gone on their 914, I have put 2 new injectors and a fuel pressure regulator and still don't have one and two cylinders firing. When I pull the plug from the injector while it is running nothing changes. I have looked and cleaned and cleaned again the grounds an I am at a loss. Maybe carb here I come. Do you think it cold be a bag ECM?

[raygreenwood]

[crodog1]

Thanks for the reply. I will pull the ecm plug this wk end and see what I come up with. Thx

[raygreenwood]

[crodog1]

Ray,

First off thank you for all the time you are spending on this. I really want to get it running right WITH the fuel infection. What is the best way to check the ground from the block spade connector to the injector plug? I am using a multi meter now. Do you have a better way? And the power side. Do I check it from the ICU plug to the plug at the injector as well. I am willing to try anything at this point. Thx Gary

[crodog1]

In looking at the wiring looks like 3,4,5 and 6 out of the ECM are the power wires to the injectors. I would think I could test there continunity and make sure the wiring part is good then look at the grounds the same way.