so, my 3500 swap is coming to an end.... cept, it doesnt seem to want to start....
itll fire with starting fluid, i though maybe the pump was going bad, that wasnt it (i clamped the return line to test, but the clamp cameoff) so with a new pump connected to test i was still getting 20psi, clamed the pressture shoots up, so now i had fuel pressure... tried to start the car, STILL wouldnt start, its like it doesnt even wana try to catch, put a volt meter on the 1 injecor i could get to without pulling the plenum and its getting something, but cant be sure of howmuch or what, digal voltmeter looks like it was htting bout 3v
so, whats the best way to test if the injectors are firing?!
20 psi is not enough, you should have close to double that pressure as the stock pressure for that engine is around 52 psi. Your best bet would be to tap into the harness with a loose injector and listen for it firing as the engine is cranked while you hold it in your hand or check out Autozone for a loaner tool that can test the circuit.
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10:07 PM
hookdonspeed Member
Posts: 7980 From: baltimore, md Registered: May 2008
20 psi is not enough, you should have close to double that pressure as the stock pressure for that engine is around 52 psi. Your best bet would be to tap into the harness with a loose injector and listen for it firing as the engine is cranked while you hold it in your hand or check out Autozone for a loaner tool that can test the circuit.
yea, im getting ~65psi now, sorry if i was confusing... hrm, loose injector... means id have to pull the rail off :/
Originally posted by hookdonspeed: yea, im getting ~65psi now, sorry if i was confusing... hrm, loose injector... means id have to pull the rail off :/
If you're not smelling raw fuel with pressure that high the injectors are not firing or your base pulse constant is so low you're not getting enough fuel but I doubt it.
If you don't have an extra injector you can use a small hose between an injector and your ear and listen for it ticking while the engine is being cranked, they are pretty loud for their size. Otherwise I'd check the ignition system to make sure you're getting the proper signal to the ecm to turn them on as well as the pump. It will prime but it will not run while cranking if the ECM does not sense spark.
[This message has been edited by Joseph Upson (edited 07-25-2011).]
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10:20 PM
hookdonspeed Member
Posts: 7980 From: baltimore, md Registered: May 2008
that parts scaring me, the one scan tool i have doesnt seem to want to communicate w/ the ecu :/
Then double check your wiring, if I recall correctly you don't need the ecm for the first design DIS ignition assembly to fire its base 10 deg setting which would account for why you're able to get it running with starter fluid.
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10:53 PM
Jul 26th, 2011
hookdonspeed Member
Posts: 7980 From: baltimore, md Registered: May 2008
Then double check your wiring, if I recall correctly you don't need the ecm for the first design DIS ignition assembly to fire its base 10 deg setting which would account for why you're able to get it running with starter fluid.
true, it gets the 7x signal directly from the sensor... ill have to double check the 24x wiring... edit: just ordered a noid light set, 8lights $15, will be usefull to keep around...
[This message has been edited by hookdonspeed (edited 07-26-2011).]
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09:00 AM
hookdonspeed Member
Posts: 7980 From: baltimore, md Registered: May 2008
Check to see if you have the 5v reference signal to your engine control sensors - low voltage will really confuse the ECU and prevent it from triggering the injectors.
You should have 12v to the injectors.
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10:06 AM
hookdonspeed Member
Posts: 7980 From: baltimore, md Registered: May 2008
Originally posted by hookdonspeed: injectors get power from the c203 *all injectors* then ground out via the ecu.
this is from darths wiring diagram (confirmed with wiring diagram from the 98venture)
That's pulsatile batch fire over 6 injectors. I just mentioned that in case you got the idea of connecting one injector for diagnostic purposes directly to 12 volts. You want to be careful not too overheat the injector coil it may not cause a problem but I've read that this can damage it. Better safe than sorry as low impedance injectors (2.5ohm) on a high impedance ECM (12-16 ohm) will burnout the drivers so it stands to reason it's important.
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08:16 AM
hookdonspeed Member
Posts: 7980 From: baltimore, md Registered: May 2008
That's pulsatile batch fire over 6 injectors. I just mentioned that in case you got the idea of connecting one injector for diagnostic purposes directly to 12 volts. You want to be careful not too overheat the injector coil it may not cause a problem but I've read that this can damage it. Better safe than sorry as low impedance injectors (2.5ohm) on a high impedance ECM (12-16 ohm) will burnout the drivers so it stands to reason it's important.
ohh no, not that crazy :P i have a 98 ecu with 06 engine, AFAIK the new 3500 injectors are the same impedance as the 3400's
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10:09 AM
phonedawgz Member
Posts: 17091 From: Green Bay, WI USA Registered: Dec 2009
I like the idea of a logic probe rather than a noid light.
The noid light shows either a flash or a no flash. On a no flash condition it really doesn't tell you much. Maybe the ECM isn't pulsing. Maybe the injector fuse is out. Maybe your noid light isn't connected properly or is just dead.
--
The logic probe, probing the ECM side of the injector will tell you:
1 - Do you have +12 with the key on engine not cranking? If so you know you have a good injector fuse and you know you are properly connected.
2 - Do you see 0v blips during cranking? If so you know the ECM is trying to fire the injector, that the ECM has a ground connected to it and that the wiring to the ECM is good.
Originally posted by phonedawgz: Plus the logic probe can be used to test other sensitive circuits since it's high impedance input puts no load on the circuit.
That was my concern, I know the injectors are high impedance, the reference between high and low impedance ECMs was to point out the significance of the subject. I think I'll pick up one of those probes though.
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11:36 AM
hookdonspeed Member
Posts: 7980 From: baltimore, md Registered: May 2008
That was my concern, I know the injectors are high impedance, the reference between high and low impedance ECMs was to point out the significance of the subject. I think I'll pick up one of those probes though.
the 98 ecu and the 3500 engine are both high impedance, idk, im thinking its gona endup being that sensor or the ecu :/
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12:29 PM
hookdonspeed Member
Posts: 7980 From: baltimore, md Registered: May 2008
so, 24x sensor was wired *correct* as per darths pinout... yet was diffrent from the pinout of the 98venture ecu im using (altho im pretty sure that interchangeable as it was still getting +12v and ground to the same pins)
now im not sure bout the sensor signal wire, from what i can tell (no scope) its reading from .8v to 1.2v to the ecu... 5v reference seems to be good where it should be...
injectors are not firing...
im bout to rip all the goddamn wires out and repin the thing again...
You need access to a diagnostic protocol for the PCM application so that you can do a step by step diagnosis. I haven't worked with anything above OBDI to avoid the MAF sensor so I can't tell you what all this PCM looks for before enabling the injectors. I like keeping it simple here, 24x ring, cam sensor, MAF sensor = not simple.
Walk away for a moment and come back, it could be something as simple as a weak/bad crank position sensor. A bad one had me about to quit my project before I discovered it was the problem then a bad MAP sensor took me to that point again. You need datalogging to help you see what the sensors are showing as you attempt to start the motor, that's what helped me find the bad MAP sensor which never set a code.
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09:13 PM
PFF
System Bot
hookdonspeed Member
Posts: 7980 From: baltimore, md Registered: May 2008
You need access to a diagnostic protocol for the PCM application so that you can do a step by step diagnosis. I haven't worked with anything above OBDI to avoid the MAF sensor so I can't tell you what all this PCM looks for before enabling the injectors. I like keeping it simple here, 24x ring, cam sensor, MAF sensor = not simple.
Walk away for a moment and come back, it could be something as simple as a weak/bad crank position sensor. A bad one had me about to quit my project before I discovered it was the problem then a bad MAP sensor took me to that point again. You need datalogging to help you see what the sensors are showing as you attempt to start the motor, that's what helped me find the bad MAP sensor which never set a code.
thats what im thinking with that .8 to 1.2v range, looks aweful low IMO.... but something else has me scared... my handheld scanner wont connect to the ecu :/ just tried that to get some sensor readings... im close to going to a 7730 ecu seriously
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09:30 PM
IFLYR22 Member
Posts: 1775 From: Tucson, AZ. Registered: May 2007
Reading through here, and not familiar with your swap at all, but does your PCM have a passkey system program in it?
Your descriptions sound exactly like my 3800 back when I put it in my 85GT and tried to start it (back in 2001). It refused to run on anything other than starting fluid. Once I found out that the PCM had passkey, I installed a bypass device and it started right up.
edited to add: I even did many of the steps you describe before I discovered the passkey issue. I did not know the 2000 GP had passkey, which was my donor engine.
-Dave
[This message has been edited by IFLYR22 (edited 07-27-2011).]
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09:41 PM
hookdonspeed Member
Posts: 7980 From: baltimore, md Registered: May 2008
Originally posted by hookdonspeed: thats what im thinking with that .8 to 1.2v range, looks aweful low IMO.... but something else has me scared... my handheld scanner wont connect to the ecu :/ just tried that to get some sensor readings... im close to going to a 7730 ecu seriously
That's a good sign something is not right at the PCM if you can't connect with a scanner.
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10:23 PM
hookdonspeed Member
Posts: 7980 From: baltimore, md Registered: May 2008
04 3500 engine running on the 98 ecu w/ stock venturevan tuning at the moment.. supposedly the 98venture did not have passkey.. *SUPPOSEDLY*
as per darth and running the vin by the dealer.
When I did mine, the 2000's were the first year of it, and not all GP's had it. Mine did. If I had it re-flashed to 1999, it would not have it. But, re-flashing back then was way more expensive than a bypass module. I ended up with a bypass module from Peripheral Electronics, and have not had an issue since. Also, my PCM does not know it is in a fiero. So I can have stock code put on it, and it will run in the car just fine.
Although,
quote
Originally posted by Joseph Upson:
That's a good sign something is not right at the PCM if you can't connect with a scanner.
That sounds like the culprit.
-Dave
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11:02 PM
hookdonspeed Member
Posts: 7980 From: baltimore, md Registered: May 2008
Originally posted by hookdonspeed: am i to assume correctly that to "bench test" an ecu, i just need always hot power, "switched" power, ground, and the 2 data lines?
When I attempted to do a bench test with a 749 ecm by just powering it up I could not datalink with it and it would not flash the engine light with terminals A&B grounded. I recall reading something about a certain number of grounds needing to be present but it was sometime ago. None the less it wouldn't work and the theory is plausible as the missing sensors left a lot of grounds open.
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11:08 PM
hookdonspeed Member
Posts: 7980 From: baltimore, md Registered: May 2008
When I attempted to do a bench test with a 749 ecm by just powering it up I could not datalink with it and it would not flash the engine light with terminals A&B grounded. I recall reading something about a certain number of grounds needing to be present but it was sometime ago. None the less it wouldn't work and the theory is plausible as the missing sensors left a lot of grounds open.
hrmmmmmmmm well if it "checks out" on our flash machine, then i may have to go over *all* my wiring :/
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11:12 PM
Jul 28th, 2011
KaijuSenso Member
Posts: 911 From: Westland, MI Registered: Jan 2007
Don't give up hope! At least you've been narrowing it down and you'll figure it out soon.
bout to plug it up to reflash to makesure itll take a flash if it does, more then likely its good.. :/ dont know of anyway other way to test an ecu out-of-car
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12:09 PM
hookdonspeed Member
Posts: 7980 From: baltimore, md Registered: May 2008
I did s 3400 swap with obd2 and a 3900 swap with obd1. I recommend staying with obd2. How close is the crank sensor to the wheel? It's external correct? I had an issue gettin gmine close enough to read on the 3900.
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09:28 PM
hookdonspeed Member
Posts: 7980 From: baltimore, md Registered: May 2008
I did s 3400 swap with obd2 and a 3900 swap with obd1. I recommend staying with obd2. How close is the crank sensor to the wheel? It's external correct? I had an issue gettin gmine close enough to read on the 3900.
im seeing voltage variance on the signal side, but not much... might be worth trying to get it closer :/
Originally posted by hookdonspeed: .050 volt variance? i was seeing close to .4 variance w/ my multimete, i just barrowed a o-scope, ill get a better look thi sweekend
Sorry, that's clearance between the trigger wheel and crank sensor.
