Injection Pulse Width

Niall Owner/Technician United Kingdom Posted   Latest   Edited  

We have a Peugeot Boxer Camper Van 1997 4 cylinder 2.0ltr petrol

This has an early fuel multi-point injection system, it is full group injection. My question is what would the expected maximum injection pulse that this or a similar system might show at full load, in this case at approx 3400rpm we get a maximum engine load of 54% and max injection pulse of 7.5ms the engine is bogged down. This has no OBD diagnostics. It looks like it has a new Cat fitted but if that was partially restricted would that cause these symptoms. I know this probably does not feature in the USA but maybe a similar system.

0
Albin Diagnostician
Washington
Albin Default
 

fuel injection pulse width is dependent on several different things, MAF inputs, or airflow calculations in case this is a speed density engine. RPM, throttle position and MAP are the most used. Anything that will choke off airflow, whether it be a throttle plate in the intake throttle body, or a throttle plate (plugged cat) in the exhaust will react pretty much the same way too. This not…

0
Default Ð Awarded
Niall Owner/Technician
United Kingdom
Niall Default
   

Hi Albin yes its a SOB over here as well, I have Pico, Flir, gas analyser (o2 not working at the moment) . The engine is a 4 cylinder 8 valve OHC, it uses a Magneti Marelli 8P-11 control system, the inlet manifold is upside down where the (cable)throttle is we have idle control stepper motor, TPS and a temperature sensor, there is a MAP sensor (no MAF) mounted remotely, it also has a charcoal…

0
Default Ð Awarded
Scott Manager
California
Scott Default
 

Hi Niall, What is the MAP KOEO and your altitude?

+1
Default Ð Awarded
Niall Owner/Technician
United Kingdom
Niall Default
 

Hi Scott the readings on the graph are from the LPG system MAP looks good there, I will check voltage from the OE MAP sensor and might be able to get the LPG to read it.

0
Default Ð Awarded
Scott Manager
California
Scott Default
 

Hi Niall, I just looked up your city altitude and it appears that you’re very near sea level. The MAP reading from your graph should be much closer to 1 Bar should it not while at WOT? This is why I was hoping to see what the Key On Engine Off MAP is.

0
Default Ð Awarded
Niall Owner/Technician
United Kingdom
Niall Default
 

Hi Scott you are correct, I'll do some more checks today, at the moment I have 992.6 hpa atmospheric pressure. The maximum recorded MAP reading through the whole graph was 1.01 bar (max min available on this LPG software very usefull) atmospheric was 1001.0 hpa but these readings are from LPG componants not the OE.

0
Default Ð Awarded
Eric Owner/Technician
Wisconsin
Eric Default
 

Pulse width alone is not going to help much. That is just how long the injector is open. Without knowing the size of the opening in the injector you have no idea how much fuel is flowing anyway. I would start with a vacuum gauge and see how it reacts to different throttle openings. Connect the vacuum gauge to a manifold vacuum port. Record the vacuum at idle, then raise the engine rpm to 2,000…

+1
Default Ð Awarded
Agree
Helpful
Alan Diagnostician
United Kingdom
Alan Default
 

If the lpg system works and the fault is present or not present when running on that, then that could help with diagnosis as the fuel filter, pump, pressure regulator and injectors are all bypassed with the lpg system operating. I think I would scope the oxygen sensor, take it for a test drive and plant the throttle so it bogs down. If the sensor goes rich it’s not likely to be fuelling and…

0
Default Ð Awarded
Niall Owner/Technician
United Kingdom
Niall Default
 

Hi Alan Yes it can be an advantage when we can bypass some petrol issues using the LPG system. In this case I need to get the petrol system running properly to get the LPG running (its worse than the petrol), the original LPG system would not re-calibrate so I have a test system temporarily installed just now. I did a quick run last night with the Pico scoping the O2 unbelievably the waveform…

0
Default Ð Awarded
Niall Owner/Technician
United Kingdom
Niall Default
 

Hi Eric I will do some more vacuum tests, one of the original problems I found was when I checked the fuel pressure it was about 15psi high, the regulator vacuum port had been soldered shut (leaking diaghram), reg too high anyway, found one with the correct relief pressure. Have not done an on road fuel pressure test yet but I would expect the injection pulse to increase with loss of fuel…

0
Default Ð Awarded
Eric Owner/Technician
Wisconsin
Eric Default
 

Unless you are monitoring the injection pulse with a lab scope I wouldn't bother looking at it or trusting it. I've never seen a computer reported data stream injection pulse that matches the actual measured injector pulse width. Instead of looking at what the computer is trying to do which may or may not be actually happening, use a sensor that reacts to the results of the fuel delivery, in…

0
Default Ð Awarded
Niall Owner/Technician
United Kingdom
Niall Default
 

Hi Eric In this case the LPG ECU is intercepting the injection pulse directly and as such would be closer to a scope reading, the LPG system which is ultimately what I need to get working uses this intercepted signal to directly operate the LPG injectors, its not that I am over focused on the pulse width. I did do a run scoping the O2 (I did not get a lean flat line) but will do another and…

0
Default Ð Awarded
Alan Diagnostician
United Kingdom
Alan Default
 

At full throttle the o2 sensor should not carry on switching. It should go to the full rich value and stay there as long as the throttle is held open.

0
Default Ð Awarded
Niall Owner/Technician
United Kingdom
Niall Default
 

Yep that's what I would expect

0
Default Ð Awarded
Niall Owner/Technician
United Kingdom
Niall Delay
 

Hi All have not been able to get time on this due to other work, but will do soon.

0
Delay Ð Awarded