Injector flow test FAIL ?, Troubleshooting lean condition Options

[jim-c]

Im working on my recent 914 purchase. 2.0L engine. D-Jet ECU . Intially the engine would fire right up and idle smooth at 1000 rpm. Unfortunately it didn’t want to rev above idle. I could quick pump the throttle and get it to rev but it was undrivable.

I have an AFR gauge and it shows dead lean when i try to rev.
I did a flow test on two injectors ( all 4 are new ) . I have 28lbs of FP .
Full throttle and crank for 15 seconds yields 2cc per injector. Supposed to be 7 ish.

Any ideas ?

Nice new harness, MPS holds vacuum and has correct impedance readings.
The balance of sensors check out okay with test procedure. Fuel pump holds 28 lbs steady and pumped a quart of gas within 30 seconds .

[JeffBowlsby]

Do you mean resistance, or inductance? Has the MPS been previously opened or adjusted?

[jim-c]

Do you mean resistance, or inductance? Has the MPS been previously opened or adjusted?

I used an ohm meter so resistance I guess . The MPS was factory sealed . Nice and shinny . I removed the cap screw yesterday. I marked both screw locations. I turned the inner screw and it affected the ARF but the engine still won’t rev up .

I have a new 123 dist. Installed . The MPS held vacuum .

[JeffBowlsby]

Too many variables here now. An adjusted MPS, new dizzy are both unknowns. It’s complicated now. Can you go back to when it did run and then make only small changes that can be reversed?

[emerygt350]

Since you have a 123 and the MPS really can be out of whack and the engine will still run "ok", I think you should a) check your timing (just to be sure) b) check to see that all injectors are firing c) disconnect the throttle switch to see if anything changes d) start to suspect the computer?

Any chance you didn't connect the trigger point wires correctly to the 123?

[jim-c]

Thanks for the replies.

I flow tested all 4 injectors. They all work and produce the same amount of fuel after 15 seconds of cranking. The amount of fuel is less than 2cc per. A very small amount.

The engine was a new install and never run, supposedly . I connected the wire harness and sensors. It fired right up and idled nicely. It just wouldn't rev. The original distributor used the crane fireball ignition. I replaced it with a new 123. It runs the same before and after new distributor .

Does the MPS control how much fuel is delivered while cranking ?

Any thoughts on the small amount of fuel on flow test ?

[jim-c]

Since you have a 123 and the MPS really can be out of whack and the engine will still run "ok", I think you should a) check your timing (just to be sure) b) check to see that all injectors are firing c) disconnect the throttle switch to see if anything changes d) start to suspect the computer?

Any chance you didn't connect the trigger point wires correctly to the 123?

I just checked the timing with a light. Got 27 total at 3500 rpm.
I installed a second unmolested MPS and it runs the same. It starts good, idles decent, won't rev unless I spray gas down the TB opening.

I double checked the distributor to trigger point harness. Matches the instructions. Usin the two outside terminals with yellow on left side looking into connector.

I disconnected the throttle switch with and there's an improvement . I'm now able to get some revs and hold it at med or high rpm. The throttle switch looks new and I adjusted it with the ohm meter. Should I remove it and take a look inside ?

[rjames]

Since you have a 123 and the MPS really can be out of whack and the engine will still run "ok", I think you should a) check your timing (just to be sure) b) check to see that all injectors are firing c) disconnect the throttle switch to see if anything changes d) start to suspect the computer?

Any chance you didn't connect the trigger point wires correctly to the 123?

I just checked the timing with a light. Got 27 total at 3500 rpm.
I installed a second unmolested MPS and it runs the same. It starts good, idles decent, won't rev unless I spray gas down the TB opening.

I double checked the distributor to trigger point harness. Matches the instructions. Usin the two outside terminals with yellow on left side looking into connector.

I disconnected the throttle switch with and there's an improvement . I'm now able to get some revs and hold it at med or high rpm. The throttle switch looks new and I adjusted it with the ohm meter. Should I remove it and take a look inside ?

Take off the cover and see if the tracks are worn. You might be able to clean them up with an eraser, or bend the arms just slightly so that they are making a better connection. If beyond repair, vendor(s) sell a replacement circuit board.

[emerygt350]

It's a super easy rebuild. I think I got mine from 914rubber. 10 minutes and you are good to go.

The only things that change volume should be duration (the MPS) and the trigger points (dizzy) and the CHT. How do you feel about your CHT? What year is it?

I assume you put the FJ67 injectors in it.

[emerygt350]

It's a super easy rebuild. I think I got mine from 914rubber. 10 minutes and you are good to go.

The only things that change volume should be duration (the MPS) and the trigger points (dizzy) and the CHT. How do you feel about your CHT? What year is it?

I assume you put the FJ67 injectors in it.

I am suspect of the throttle switch really contributing though. It should have no effect on static flow on those injectors. It really is just an accelerator pump. It is supposed to tell the system when the car is 'idling' though. I suspect the disconnect just made the computer a little confused and that helped richen the mix (no longer thinks it is idling and is taking information from the MPS at closed throttle).

[JeffBowlsby]

I am struggling to understand the low fuel flow and how it may be related to the lean condition.

Did you change the fuel lines under the tank recently? Is there a kink in the lines? Does your FP drop or is it steady? Is the filter sock in the tank dirty? Clogged fuel filter?

[jim-c]

I am struggling to understand the low fuel flow and how it may be related to the lean condition.

Did you change the fuel lines under the tank recently? Is there a kink in the lines? Does your FP drop or is it steady? Is the filter sock in the tank dirty? Clogged fuel filter?

I have not removed tank to check it out. Yet.

The FP gauge is rock steady. Im going to pull the return line and see how much gas the FP delivers. I did a quick test yesterday and it filled a quart bottle in 15 seconds.
The pump and filter are not original but new. I didn't know about a sock filtering the tank.
Can I assume a flow test will determine the state of all these items ?

[rhodyguy]

The fuel sock lives in the bottom of the tank. If not fully fouled, as demand increases delivery decreases. It will suck flat. With a drained tank you can look down the fill opening with a flashlight to see it's condition. The sock should be standing up. Not flattened and laying down. Pumping the tank empty is easy with facet pump, some lengths of fuel line, a battery and a catch container. A BIG catch container.

[rjames]

The fuel sock lives in the bottom of the tank. If not fully fouled, as demand increases delivery decreases. It will suck flat. With a drained tank you can look down the fill opening with a flashlight to see it's condition. The sock should be standing up. Not flattened and laying down. Pumping the tank empty is easy with facet pump, some lengths of fuel line, a battery and a catch container. A BIG catch container.

You can use a jumper on the relay board to keep the fuel pump running in the car with the ignition on and engine off. When I drained my tank I just pumped the remaining gas into the tank of another vehicle. Just make sure to shut off the pump when the fuel is gone so the pump doesn't burn out.

[914Mels]

Im working on my recent 914 purchase. 2.0L engine. D-Jet ECU . Intially the engine would fire right up and idle smooth at 1000 rpm. Unfortunately it didn’t want to rev above idle. I could quick pump the throttle and get it to rev but it was undrivable.

I have an AFR gauge and it shows dead lean when i try to rev.
I did a flow test on two injectors ( all 4 are new ) . I have 28lbs of FP .
Full throttle and crank for 15 seconds yields 2cc per injector. Supposed to be 7 ish.

Any ideas ?

Nice new harness, MPS holds vacuum and has correct impedance readings.
The balance of sensors check out okay with test procedure. Fuel pump holds 28 lbs steady and pumped a quart of gas within 30 seconds .

Is the manifold pressure sensor hose clear? Are you getting correct vacuum readings at idle? At idle if you induce a vacuum leak at the pressure sensor hose does that richen up the mixture?

[jim-c]

The fuel sock lives in the bottom of the tank. If not fully fouled, as demand increases delivery decreases. It will suck flat. With a drained tank you can look down the fill opening with a flashlight to see it's condition. The sock should be standing up. Not flattened and laying down. Pumping the tank empty is easy with facet pump, some lengths of fuel line, a battery and a catch container. A BIG catch container.

Thanks. I will do this today.

[jim-c]

Is the manifold pressure sensor hose clear? Are you getting correct vacuum readings at idle? At idle if you induce a vacuum leak at the pressure sensor hose does that richen up the mixture?
[/quote]


I will check this today. I haven't put a vacuum meter on it yet .

[jim-c]

Progress update .

Tank sock filter was vertical. I pulled and cleaned the tank and filter.
Installed a new fuel pump and filter for good measure.

Injector test still shows very small amount of fuel being delivered.

A second ECU installed, no change. Second MPS installed , no change.

I pulled the ECU Harness and checked continuity and resistance to correct connectors, checks good.

I pulled the injectors for testing and cleaning. Cleaned injector tubes and will install new fuel line .

Vacuum gauge shows 10 hg when trying to idle. I still need to induce leak to see if mixture goes rich.

[emerygt350]

Progress update .

Tank sock filter was vertical. I pulled and cleaned the tank and filter.
Installed a new fuel pump and filter for good measure.

Injector test still shows very small amount of fuel being delivered.

A second ECU installed, no change. Second MPS installed , no change.

I pulled the ECU Harness and checked continuity and resistance to correct connectors, checks good.

I pulled the injectors for testing and cleaning. Cleaned injector tubes and will install new fuel line .

Vacuum gauge shows 10 hg when trying to idle. I still need to induce leak to see if mixture goes rich.

Interesting. Should be at 17ish for idle but that still doesn't address the lackluster injectors.

[914sgofast2]

Low idle vacuum is likely a timing problem or undiscovered vacuum leak. Also, do you have the correct 123 Distributor that is set up to run with Djet? Not all the 123 Dizzys are compatible with Djet. You could be running on the cold start injector only if the 123 Dizzy is not sending the correct pulse signal to your ECU to fire the injectors.

Low fuel pressure could be a kinked rubber fuel line hose (or metal pipe) somewhere in the fuel system between the tank and the engine; or a faulty fuel pressure regulator that is stuck slightly open and sending a lot of the gas back to the tank.

Failure of fuel pump to run long enough is going to be a wiring (or internal ignition switch failure) or an ECU problem.