Injector Voltage

[whitetiger]

I have no injector spray....

injector 1 12v on both
injector 2 12v and 1v
injector 3 12v and 1v
injector 4 12v and 1v

ECU wires 51-52-60-61 all have 12v+
mpfi relay good
mpfi fuse good
new fuel pump
new filter
rail has fuel pressure


how do I fix?

 

[steve]

While waiting for Steve to get back with some more specific info I'm trying to figure out why you would have 12v on both sides of the injectors if that was while cranking?

If I understood correctly the only time he was measuring chile cranking he saw "the voltage flux from lowest of 0 to highest of 12v - but most of the low voltage is in the 2-4v range. I assume this to be the ECU pulsing faster that what my meter reads" The assesment that the meter isn't fast enough would be correct your going to need a scope to see the 2ms pulses to ground and what your meter reads will have to do with how it averages DC voltages. Everything else I assumed to be measured with just the key turned on to power the MPI system.

I would be interested in knowing why the engine crankshaft sensor would not play a roll in starting. It would seem to me that the later ECU which you have, would be looking for this input and not finding it would possibly cause the problem you are having. Maybe when this gets solved I'll be up to speed.

Based on the engine sparking and firing up briefly when it had something to burn inplys that the CAS is working at least partually. There isn't any sigificant difference in 1G CAS signals and we have never noticed any compatability issues between ECU's and CAS's.

We were talking about the tachometer signal, which you might be confusing with the engine crankshaft sensor. The Tach signal is generated from the coils primary by either the tach sender in the coil pack on '90 cars or the Power Transistor Module on 91+ cars.

That sender gates the pulsating coil primarys and sends it back to the tach gauge and the ECU. The ECU uses that to check that the coils are firing and throws a 44 CEL if it fails. The Gauge uses the signal to display RPMs and there is a compatability issue here with using later ECU's in '90 cars. The 91+ cars aren't bothered by having a '90 ECU instead of the correct one other than the generic swapped pins for IPS and MAF reset.

Steve

 

[whitetiger]

I will try soaking the injectors again.

what are the chances all 4 injectors are still stopped up after extensive soaking and cleaning???

 

[steve]

I'm not getting a CEL at all - ever - key on, off, acc, or at start position

You should be getting a CEL light right after you first turn the ignition on during the light test for the other I-lights. It should be on for several seconds and go off.
If it doesn't you need to check that the bulb isn't burned out or that this part of the harness is correct. If the bulb goes on when you ground ECU pin 64 then the ECU isn't booting or that ECU has a problem with it's CEL circuit. I've fixed a couple that had bad CEL circuit traces.

Steve

 

[steve]

I will try soaking the injectors again.

what are the chances all 4 injectors are still stopped up after extensive soaking and cleaning???

I don't know, how long did that have to varnish up?
Places that clean injectors do it while applying injector pulses to free them up.

The basic laws of physics require a magnetic field to be generated when a current passes through a coil. You can measure the current being drawn like I did. What we have is a voltage divider once the ECU side is grounded, made up of the injector resistor and the DC resistance of the injector coil and we can calculate the voltage drops and compare.

Since we've taken the ECU out the mix by grounding the injector directly it should fire, if it doesn't the finger points at the injector until we get new data.

Steve

 

[GTM]

I would like you to do a test just to humor me. Using a good quality test light like Snap On or similar can be found at Harbor Freight, attach the clip to the B+ of the battery. With the key OFF probe the injector wires, one side will do nothing the other will fire the injector. It won't really fire, IT will hold it wide open until you remove the probe. No if and but or nor for's about it. If you use too small a bulb it won't fire, too large possible coil damage. It WILL flood the engine if you have pressure in the fuel rail. You can test all 4, they should make click noise, if you have a pressure gauge in the system you can watch it drop. You will have to remove plugs and crank to clear the fuel.

To test for start, with the injectors unplugged or no pressure spray _starting fluid_ in through the throttle plate and work the throttle by hand as needed while someone operates the starter. Always stand to the side in case of backfire into intake while spraying. Use the Chemtool _after_ it starts.
...................

I don't know what's in the cleaner you have used but here are some solvents which should clean injectors, MEK, trichlor, methylene chloride, perchlor, and acetone, I think MEK or MEKP will be the most corrosive. Tri and Per are used in vapor degreasing and ultra sonic cleaners and for some dry-cleaning. Use standard shop practices when using any strong solvent.

Let us know what happens.

Cheers,
GTM

 

[whitetiger]

I rigged a "bench test" for the injectors - they fire just fine.

the CEL is fine - bulb was out, I now know the ECU is booting fine.
(I also ordered a datalogger cable)

the voltage matches at both the injectors and the ECU
12.2v with key on
4~12 while cranking

but the injectors still do not fire. I'm guessing low amperage?

you guys have any ideas? I'm completely lost as to where to go next.

thanks for all the help getting me this far.

 

[GTM]

I rigged a "bench test" for the injectors - they fire just fine.

the CEL is fine - bulb was out, I now know the ECU is booting fine.
(I also ordered a datalogger cable)
the voltage matches at both the injectors and the ECU
12.2v with key on
4~12 while cranking
but the injectors still do not fire. I'm guessing low amperage?
you guys have any ideas? I'm completely lost as to where to go next.
thanks for all the help getting me this far.

I guess you decided to not humor me with the test light and the starter fluid. It's 5 minutes out of your life.

Have you tried interrogating the rodents?

Cheers,
GTM

 

[steve]

I rigged a "bench test" for the injectors - they fire just fine.

the voltage matches at both the injectors and the ECU
12.2v with key on
4~12 while cranking

but the injectors still do not fire. I'm guessing low amperage?

I went and check my injector resistor pack. I get 6.4 ohms per resistor.
To be conservative lets say it's 8 ohms and 3 ohms for the injector and we'll assume the transistor driver is weak and can only pull down to 1V.
At 12V battery we are going to have 1 amp flowing through the injectors. ((12 - 1) / (8 + 3))
My test setup from the other day fired the injector on 0.5A What did your do?

The voltage at the resistor side of the injector should go from battery voltage to:
Vout = ((Vin * Rinjector)/(Rresistor + Rinjector)) = 3v + 1 since we assumed the transistor was only pulling down to 1v.

Since you see the voltage pulsing at both the injector and the ECU, I'm at a loss as to why the injector isn't firing unless you have some huge fuel pressure holding it closed.

Steve

 

[whitetiger]

after only a few cranks of the motor i touch the resitor box - it was extremely hot. I have another resistor box on the way (91 honda civic) I beleive they are the same. will update later this afternoon.

left my voltohm meter at work (dangit) will get resistance and voltage measurements later.

 

[whitetiger]

my datalogger gives me a code 41 "Injector Curcuit" and that's the only error anywhere.

the civic resistor box didn't work.....

 

[steve]

Make sure you don't have the same problem 4g63tsiawd had with the TPS and resistor connectors swapped.

http://www.dsmtuners.com/forums/showthread.php?p=1453019#post1453019

Steve

 

[GTM]

my datalogger gives me a code 41 "Injector Curcuit" and that's the only error anywhere.

the civic resistor box didn't work.....

My hair is falling out and I can't sleep.

Are you still using the wrong ECU they sold you? The test light should be able to help isolate some of your problems if you give it a chance.

Cheers,
GTM

 

[whitetiger]

the only thing I can find is pin 13 on the ecu isn't plugged to anything under the hood... on the pinout it says "power" not "power supply" so I am hesitant to put constant 12 to it..

anyone know where pin 13 ultimately ends up?

 

[4g63tsiawd]

Yeah man I sent you a pm, see if the two are swapped that the same code I was getting and it is injector circuit open.

 

[whitetiger]

I wish it were swapped connectors!!!! I already checked that.
error 41 injector curcuit...traced the curcuit as a whole and the only issues with in it are with pin 13 on the ecu.
it also ties into the mpfi relay and most likely the ignition switch.

 

[GTM]

I wish it were swapped connectors!!!! I already checked that.
error 41 injector curcuit...traced the curcuit as a whole and the only issues with in it are with pin 13 on the ecu.
it also ties into the mpfi relay and most likely the ignition switch.

Simple basic continuity tests have to be made with a data logger(not). Maybe it's time to pay someone that's done this for a living. This is so frustrating for you seem to be trying to think this problem to death.

Pull the harness at ECU, at harness plug continuity check circuit for each injector. It has to go out and come back for a complete circuit. It doesn't matter which pin is going to be ground and which you probe with the stupid test light attached to +. I HAS to light or you have a problem. Simple, no if and buts about it. It's not rocket science, you got dozens of more complicated circuits.

Eliminate _1_ thing at a time, make index cards for each thing you check and determine it passes or fails or don't know. Put the don't know at the back and go on to the next. Work smarter not harder. This is a lousy 2 hour job at best but you seem to be jumping from thing to another before you have confirmed it's condition.

This reminds me of the guy a while back that had everybody going in circles only to find out his battery was dead.

GTM

 

[steve]

I wish it were swapped connectors!!!! I already checked that.
error 41 injector curcuit...traced the curcuit as a whole and the only issues with in it are with pin 13 on the ecu.
it also ties into the mpfi relay and most likely the ignition switch.

Pin 13 is the sense line from the fuel pump power lead coming off pin 2 of the MPI relay.
The ECU checks it when it's turned the fuel pump on and throws a 44 error is it doesn have battery voltage.

The ignition switch has two signals to the ECU. The first is pin 110 from the run position telling the ECU to power up. The second is from the start position via the starter relay on pin 108 informing the ECU that the engine is cranking.

Steve

 

[whitetiger]

injectors check
harness just checked again (ecu to injectors Check) (resistor box to injectors Check)
ecu - unkown (logger connects and gives all data properly) I assume it's fine.
mpfi fuse check
mpfi relay - unknown now... it is clicking so I assume it's good.
(mpfi relay - is it dual relay?
resistor box checks just like steve's

I even plugged it all up and check the connectors to insure I didn't have faulty connections.

My grounds are good.
I have fuel pressure... PSI unknown
all fuel lines clear
new fuel filter
plenty of spark (new plugs and wires)



maybe my mpfi relay is only half working... I do hear it click but noticed it was a dual relay while looking at the pinout...
how can I test this relay properly?

note: there was an extra mpfi relay in the car when I got it... *sigh*

thanks for the help

 

[steve]

mpfi relay - unknown now... it is clicking so I assume it's good.
(mpfi relay - is it dual relay?

maybe my mpfi relay is only half working... I do hear it click but noticed it was a dual relay while looking at the pinout...
how can I test this relay properly?

note: there was an extra mpfi relay in the car when I got it... *sigh*

Yes, there are two relays inside the box.
One controls the MPI power and has a single coil and a common power feed to the contacts and coil on pin 10. Pin 8 is the ground side of the coil and pins 4 & 5 are the NO contacts.

The second relay controls the fuel pump power and it has two coils. Pin 9 and pin 6 are one coil normally connected in the starter circuit. The other coil has a commpn power feed on pin 3 with the other end of that coil at pin 7 which normally goes to ECU pin 63.The NO contact is pin 2.

To test you energize a coil and check the the contacts close. for the coils with common feeds this means seeing +12 on the contacts after applying +12 to the common and grounding the other side of the coil. For the starter coil, it means continuity between 3 and 2 when +12 is applied to 9 and pin 6 is grounded.

Steve

 

[whitetiger]

(12.2-1)/(6.2+2.6)=1.28 amps on injectors, btw

 

[steve]

(12.2-1)/(6.2+2.6)=1.28 amps on injectors, btw

If you had a scope you'd see that the ECU get's a lot closer to ground that the 1v I used as an example, like within a few tenths. And when the car is running the battery voltage is around 13.8. I've totally ignored as well the effect of the injectors inductance in the calculations.

Steve

 

[whitetiger]

tell me how to test the relay like I'm 10!!!

put 12+ on what and 12- on what to get click.....

 

[whitetiger]

what is the value of the resistor insid ethe mpfi relay?

 

[GTM]

tell me how to test the relay like I'm 10!!!

put 12+ on what and 12- on what to get click.....

I am unsubscribing. get a book.

 

[whitetiger]

awww GTM I was just jokin around man... I'm trying to stay in good humor. I guess I should of used smilies or something.



back to the issue at hand. the mpfi relay --- all 3 coils operate when energized manually. Next I'll test the wiring going into the mpfi relay and make sure each has it's proper voltage.

mpfi relay: pin 10 12+ pin 6 ground energizes coil.
pin 5 12+ pin 4 gound energizes coil.
pin 2 12+ pin 8 ground energizes coil.


beyond this I really can't see going any further. I mean there are only so many places you can look for a injector curcuit problem. And I'm comfortable that we've covered them all in full detail in this thread.

I've taken the harness out and traced and test lighted all of it by help of the pinout.
tested injectors
tested mpfi relay
tested the resistor box
all thats left is the ecu... which is new.