DME Cutting Power To Injectors - GOOD FUEL PRESSURE
05-10-2024 | 10:41 PM
#61
Burning Brakes
Joined: Sep 2021
Posts: 886
Likes: 214
From: Phoenix area
I looked at all the 944 schematics. The only ones with resistors, which are in the positive side, are the 4-valve engines. And the last year, the '91 944S, they were deleted as well. I just can't imagine someone opening up a DME and adding resistors internally in order to make the wrong injectors work. I would like to know what the voltage does on the red/blue wires on the injectors, referenced to ground, while you are cranking. This one measurement will let us know if the issue is on the positive side of the injector, or the negative side. It should drop very little.
05-11-2024 | 09:14 AM
#62
Burning Brakes
Joined: Nov 2001
Posts: 1,217
Likes: 14
From: Somerset UK
05-11-2024 | 10:08 AM
#63
Burning Brakes
Joined: Nov 2001
Posts: 1,217
Likes: 14
From: Somerset UK
05-11-2024 | 01:04 PM
#64
Thread Starter
Intermediate
Joined: Dec 2021
Posts: 38
Likes: 0
From: Dayton, Ohio
I looked at all the 944 schematics. The only ones with resistors, which are in the positive side, are the 4-valve engines. And the last year, the '91 944S, they were deleted as well. I just can't imagine someone opening up a DME and adding resistors internally in order to make the wrong injectors work. I would like to know what the voltage does on the red/blue wires on the injectors, referenced to ground, while you are cranking. This one measurement will let us know if the issue is on the positive side of the injector, or the negative side. It should drop very little.
05-11-2024 | 01:10 PM
#65
Thread Starter
Intermediate
Joined: Dec 2021
Posts: 38
Likes: 0
From: Dayton, Ohio
no need to bite my head off buddy... just trying to offer you some helpful advice.
Q.1 If the car runs ok with all the original injectors fitted why are you screwing around with it ?
Lets have a look at what we know
Problem as I understand it.
...The ECU or DME (whichever you prefer,) is cutting fuel to the injectors .
The engine starts and runs with one (any one ) of the injectors disconnected.
9 times out of 10 that almost always points to an over-fuelling situation .....whether due to problems with one or more of the fuel delivery components or the DME pulsing more fuel than the engine requires because it is receiving incorrect information .
So we know that this issue HAS to involve the fuel delivery system ....but it could just be the symptom !.....and the cause could involve some other component/s .
So first we should test and eliminate the mechanical components of the fuel delivery system . Injectors , FPR Damper, Fuel pump, Fuel Filter ,etc
if they all test ok then next we should check and test all the control components of the fuel delivery system.......DME Relay , AFM, TPS, Speed Sensor, Crank sensor, Engine coolant Temperaure sensor, Throttle body Air Idle Control valve if fitted .including testing all the associated wiring .
lastly if all that checks out then we are looking at the DME .and the DME should never be touched until all of the other checks and test are carried out first in the correct sequence . It is too expensive a component for a layperson to screw around with and potentially damage. A simple exchange test with a known good DME would be the first step before messing with it.
Hope that is helpful...Remember we are trying to help you from the other side of the World without the benefit of seeing your car and relying totally on the information that you are providing us with good luck johnny
Q.1 If the car runs ok with all the original injectors fitted why are you screwing around with it ?
Lets have a look at what we know
Problem as I understand it.
...The ECU or DME (whichever you prefer,) is cutting fuel to the injectors .
The engine starts and runs with one (any one ) of the injectors disconnected.
9 times out of 10 that almost always points to an over-fuelling situation .....whether due to problems with one or more of the fuel delivery components or the DME pulsing more fuel than the engine requires because it is receiving incorrect information .
So we know that this issue HAS to involve the fuel delivery system ....but it could just be the symptom !.....and the cause could involve some other component/s .
So first we should test and eliminate the mechanical components of the fuel delivery system . Injectors , FPR Damper, Fuel pump, Fuel Filter ,etc
if they all test ok then next we should check and test all the control components of the fuel delivery system.......DME Relay , AFM, TPS, Speed Sensor, Crank sensor, Engine coolant Temperaure sensor, Throttle body Air Idle Control valve if fitted .including testing all the associated wiring .
lastly if all that checks out then we are looking at the DME .and the DME should never be touched until all of the other checks and test are carried out first in the correct sequence . It is too expensive a component for a layperson to screw around with and potentially damage. A simple exchange test with a known good DME would be the first step before messing with it.
Hope that is helpful...Remember we are trying to help you from the other side of the World without the benefit of seeing your car and relying totally on the information that you are providing us with good luck johnny
05-11-2024 | 03:45 PM
#66
Burning Brakes
Joined: Sep 2021
Posts: 886
Likes: 214
From: Phoenix area
05-11-2024 | 04:39 PM
#67
Burning Brakes
Joined: Sep 2021
Posts: 886
Likes: 214
From: Phoenix area
Thinking even more, it would be also useful to have the voltage drop from the battery to the injector with the ignition on but not cranking. This will be the voltage drop due to the DME power draw by itself.
Last edited by orig944; 05-12-2024 at 11:23 AM.
05-14-2024 | 06:53 PM
#68
Thread Starter
Intermediate
Joined: Dec 2021
Posts: 38
Likes: 0
From: Dayton, Ohio
Just an update for anyone following, I currently have the high z injectors in the car while I fine tune basically everything on the car. As soon as I finish all the tiny fixes I'm making now, I'll be throwing the low z injectors back in and hunting it down again. Should be next weekend I get them back in. It would be great to have a good list of ideas to check out when the time comes.
05-15-2024 | 11:01 AM
#69
Three Wheelin'
Joined: Oct 2021
Posts: 1,404
Likes: 313
From: Southern WI - 89S2 Megasquirt PNP
Swap a DME with the same part number or just run it with high impedance injectors.
Or as others mentioned try genuine bosch injectors with matching/correct part numbers
Or as others mentioned try genuine bosch injectors with matching/correct part numbers
05-15-2024 | 01:10 PM
#70
Burning Brakes
Joined: Nov 2001
Posts: 1,217
Likes: 14
From: Somerset UK
of apparently making everything as incredibly complicated as possible.................
rather than chose the obvious and straightforward.
05-15-2024 | 01:23 PM
#71
Thread Starter
Intermediate
Joined: Dec 2021
Posts: 38
Likes: 0
From: Dayton, Ohio
Okay so then send me 4 genuine injectors by this weekend. Thanks. Or maybe just understand some people work with what they have. I'm not a purist like you, so I don't have to cry and throw a fit about an aftermarket part. I just fix problems, in the most logical way. You would have already thrown $4k at this problem and still wouldn't have a running vehicle. I'll fix the root cause and have a running vehicle....the exact same way I have over the last 3 years and have it in running and driving condition. These cars aren't worth anything, it makes absolutely no sense to throw a **** ton of money at a car that's worth $6-7k in pristine condition. I don't know what it is about these vehicles that make people think they're worth anything. It is an early model non turbo with basically no options my guy, it's just not worth spending the money on ridiculously expensive parts that aren't the actual problem. This is not my first restoration, I've restored vehicles that are actually worth any money at all, those ones are the ones that get genuine OEM parts, not this.
05-15-2024 | 01:28 PM
#72
Thread Starter
Intermediate
Joined: Dec 2021
Posts: 38
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From: Dayton, Ohio
I was lucky enough to find someone not too far that's willing to supply a known good DME this weekend, so will be trying that. That same person may or may not have a set of original injectors I'll be able to try as well. I'll report back on Monday with the results.
05-15-2024 | 01:34 PM
#73
Three Wheelin'
Joined: Oct 2021
Posts: 1,404
Likes: 313
From: Southern WI - 89S2 Megasquirt PNP
Let us know what you find out, hopefully reveals some insights
05-15-2024 | 04:48 PM
#74
Burning Brakes
Joined: Nov 2001
Posts: 1,217
Likes: 14
From: Somerset UK
Wow you sure know how to throw all your toys out of the pram don't you ...
You clearly haven't made the slightest attempt to look at my previous posts and see what my approach is to rectifying non start and hard running issues are otherwise you'd know that I always always take owners through a sequential testing and checking process that costs absolutely nothing.... nada... nil... zilch... $0
If you cannot afford to buy a set of used injectors for one of the most common sports cars found in a breaker yard then perhaps you should consider buying something that you can afford and that actually runs . If you can't afford a set of injectors, how on earth are you going to afford the Insurance and other costs associated with running and maintaining a 40 year old Classic car ???? .Why anyone would buy a car without injectors and then try and fit some from a completely different car beats me,
?
You clearly haven't made the slightest attempt to look at my previous posts and see what my approach is to rectifying non start and hard running issues are otherwise you'd know that I always always take owners through a sequential testing and checking process that costs absolutely nothing.... nada... nil... zilch... $0
If you cannot afford to buy a set of used injectors for one of the most common sports cars found in a breaker yard then perhaps you should consider buying something that you can afford and that actually runs . If you can't afford a set of injectors, how on earth are you going to afford the Insurance and other costs associated with running and maintaining a 40 year old Classic car ???? .Why anyone would buy a car without injectors and then try and fit some from a completely different car beats me,
?
05-15-2024 | 04:57 PM
#75
Thread Starter
Intermediate
Joined: Dec 2021
Posts: 38
Likes: 0
From: Dayton, Ohio
Wow you sure know how to throw all your toys out of the pram don't you ...
You clearly haven't made the slightest attempt to look at my previous posts and see what my approach is to rectifying non start and hard running issues are otherwise you'd know that I always always take owners through a sequential testing and checking process that costs absolutely nothing.... nada... nil... zilch... $0
If you cannot afford to buy a set of used injectors for one of the most common sports cars found in a breaker yard then perhaps you should consider buying something that you can afford and that actually runs . If you can't afford a set of injectors, how on earth are you going to afford the Insurance and other costs associated with running and maintaining a 40 year old Classic car ???? .Why anyone would buy a car without injectors and then try and fit some from a completely different car beats me,?
You clearly haven't made the slightest attempt to look at my previous posts and see what my approach is to rectifying non start and hard running issues are otherwise you'd know that I always always take owners through a sequential testing and checking process that costs absolutely nothing.... nada... nil... zilch... $0
If you cannot afford to buy a set of used injectors for one of the most common sports cars found in a breaker yard then perhaps you should consider buying something that you can afford and that actually runs . If you can't afford a set of injectors, how on earth are you going to afford the Insurance and other costs associated with running and maintaining a 40 year old Classic car ???? .Why anyone would buy a car without injectors and then try and fit some from a completely different car beats me,
?Edit: My apologies to anyone else actually paying attention/getting notifications to the thread, I'm done responding to these comments and will keep it content focused from here.
Last edited by Jman2678; 05-15-2024 at 04:58 PM. Reason: Edit:
