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Old 10-09-2012, 12:15 PM   #1
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Default Fuel pump does'nt stay primed

Hi,
I recently swapped a 2002 BP in my 1990 MSI.
When I try to start the engine, I hear the fuel pump priming for 2 seconds then it stop.
I test put a timing light onto the first sparkplug and it showed me 1 or 2 spark while cranking.

I don't know why the fuel pump stop priming and when I did the datalog, I got around 60 psi for the fuel pressure.

Did anybody know what could this be?

-Did I inverted my fuel lines? (does the pump have a overpressure switch and turns off when it reachs a certain pressure for a certain periode of time?)



****
Here is the datalog in question (the TPS was not plugged and I did took the time to make a nice DataLogViewer)
I uploaded it in CSV and PDF
Attached Files
File Type: csv datalog-absRTP-oct08-2012-csv.csv (12.8 KB, 72 views)
File Type: pdf datalog-absRTP-oct08-2012.pdf (281.4 KB, 227 views)
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Old 10-09-2012, 12:19 PM   #2
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how is your fuel pump wired to the MS?
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Old 10-09-2012, 12:20 PM   #3
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With the MSI trick for 1990s (green wire or something like this if I can remember well), directly to ignition, under the steering column
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Old 10-09-2012, 01:07 PM   #4
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You mean directly to the fuel pump relay

does it run if you jump f/p and gnd in the diagnostics box?
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Old 10-09-2012, 01:56 PM   #5
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I'll have to give it a try,

What is the regular fuel pressure in our engine? 60-63 psi? or lower?
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Old 10-09-2012, 02:01 PM   #6
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should be 35psi at idle and around 45-50psi at atmospheric
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Old 10-09-2012, 02:04 PM   #7
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Hmmm, I think I will have to check if I plug my fuel line correctly,
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Old 10-15-2012, 12:01 PM   #8
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The normal behavior of the MegaSquirt is to prime the fuel system for 2 seconds after key on, then shut off the fuel pump unless there is a valid incoming RPM signal.
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Old 10-15-2012, 02:13 PM   #9
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Yeah, this sounds like a trigger problem to me. The MS may simply not be reading the crank / cam sensors. When you made the swap, did you transfer the CAS from the old engine to the new one, or have you re-wired for the '02 engine's discrete crank and cam sensors?

Why don't I see RPM in that log? I don't mean that it's zero, I mean the column for it is missing.



Also, ignore the fuel pressure indication in MS. Unless you have actually installed a fuel pressure sensor and connected it to the MS, this reading is completely bogus.
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Old 10-16-2012, 05:25 PM   #10
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Quote:
Originally Posted by Joe Perez View Post
Yeah, this sounds like a trigger problem to me. The MS may simply not be reading the crank / cam sensors. When you made the swap, did you transfer the CAS from the old engine to the new one, or have you re-wired for the '02 engine's discrete crank and cam sensors?

Why don't I see RPM in that log? I don't mean that it's zero, I mean the column for it is missing.



Also, ignore the fuel pressure indication in MS. Unless you have actually installed a fuel pressure sensor and connected it to the MS, this reading is completely bogus.
You don't see rpm because I took it off because it was 0

So I guess I have my problem, no trigger.

I kept my CAS and put it on the exhaust side.

Now I have a new thing to look at!!

Thank you Ben and Joe!
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Old 10-16-2012, 05:36 PM   #11
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Well, on the plus side, it's probably a simple fix then. Most likely a CAS-related wire got cut / broken / squished / not plugged in during the swap.


During cranking, you should read somewhere in the vicinity of 200-300 RPM on the MS, assuming a healthy battery and starter. Until you achieve that, nothing is going to work.

Tip: while you're troubleshooting, remove the spark plugs and disconnect the primary (low-voltage) side of the ignition coils. This will greatly decrease the load on the battery and starter. Also, disconnect the electrical plug for the fuel injectors, so that you're not constantly spraying fuel into the chambers. (The injectors fire once every time you turn on the ECU, regardless of whether the rest of the system is working or not.)

Your dashboard tach may not be working either, but don't worry about that for now. It's the tach in TunerStudio / MegaTune that you need to worry about.
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Old 10-16-2012, 10:18 PM   #12
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Wouah!!

Thanks Joe!

I really appreciate the time you took to guide me!

I'll give it a try saturday
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Old 10-20-2012, 01:52 PM   #13
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Ok, so I checked the continuity between the 4 wires between the CAS and the ECU and I have not short circuit or broken wires.


The big white/red is 12V, the black/green is Ground, the Yellow/blue is one of the input (CAM or CRANK) and the white is the other one (Crank or cam)

I tested the fonctionnality of the CAS by turning the engine by hand when the ignition on, when I place the Voltmeter between ground and the Yellow/Blue wire I have readings between 0.6V and 6.4V (which I guess is 0V and 5V)

But when I try to find a reading between the white one and ground, I have one reading, a steady 0.4V.

I think I found my problem, but I don't know what to do, is it the CAS that is broken?

I guess I should try to use the BP-Z3 cam sensor and crank sensor....


I'm working on this all day long, I would appreciate a quick answer from of you.

Thank you
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Old 10-20-2012, 03:17 PM   #14
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Quote:
Originally Posted by absRTP View Post
But when I try to find a reading between the white one and ground, I have one reading, a steady 0.4V.

I think I found my problem, but I don't know what to do, is it the CAS that is broken?
Assuming you have continuity all the way across the white wire (from CAS to ECU) and it is not shorted to ground, the CAS is likely at fault.

To rule out an ECU or wiring fault, disconnect the CAS and measure between the white wire and ground at the harness connector where the CAS would normally plug in. You should see +5 here with the key on. If not, it's an ECU or wiring problem. If you do see +5 here with the CAS disconnected, but it goes down to 0v constantly with the CAS connected, it's a bad CAS.



Quote:
I guess I should try to use the BP-Z3 cam sensor and crank sensor....
The MS1 CPU does not support the NB-style crank or cam pattern. You must use an NA CAS (or a fixed-pitch crankwheel such as a 36-1) with the MS1 CPU.
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Old 10-20-2012, 11:05 PM   #15
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Ok, I tested the yellow and the white wire, I have 5 volt between the Yellow wire and the ground but I have 0V between the White one and the ground.

I will look at the RPM circuit in the megasquirt and double check my wiring harness.

Thanks alot Joe for the quick input
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Old 10-21-2012, 04:34 PM   #16
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I think I found the problem,

according to the V3 schematic

https://www.miataturbo.net/attachmen...1&d=1350847929

I have no continuity between OPTOIN and D1, maybe a trace is burned somewhere, I'm trying to find the gerber files of the board before jumping optoin to D1.
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Fuel pump does'nt stay primed-sche.jpg  
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Old 10-21-2012, 04:43 PM   #17
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Quote:
Originally Posted by absRTP View Post
I'm trying to find the gerber files of the board before jumping optoin to D1.
Good luck with that. So far as I'm aware, the artwork has never been released.

OTOH, this is only a 4 layer board, and I'm 99% certain that the inner layers are nothing but power and ground planes, so it should be easy to trace visually.
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Old 10-21-2012, 04:45 PM   #18
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Actually that trace goes semewhere in the middle layers.... I haven't found where it is suppose to go...

Well, I know it should end at D1, but since I don't have continuity and if I remember well, I acidentaly removed to solderpad from one end of D1 while unsoldering it (then I jumped D2 and everything worked fine, until now)
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Old 10-21-2012, 04:46 PM   #19
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Quote:
Originally Posted by absRTP View Post
Actually that trace goes semewhere in the middle layers.... I haven't found where it is suppose to go...
?

You're certain it's not just a via from top to bottom?
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Old 10-21-2012, 05:02 PM   #20
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There is a via (on the left of the "G" from grippo) but there is nothing except the via on the other side and when I place a bright light under it, I can see the trace going somewhere from either layer 2 or 3.



I circled it out on these 2 pictures of my board (note the ugly jump for my D1 and D2)

On this picture you see the trace from OPTOIN going to the via next to the G from Grippo:


On that picture, the trace ends at this via:
Attached Thumbnails
Fuel pump does'nt stay primed-2b59a6f0-3209-4856-b82b-99c9f7e9729b-2646-0000039268d5c195_zps8ff6803a.jpg   Fuel pump does'nt stay primed-da2d6a92-cf1b-4c2a-bbcc-24e660ec2553-2646-000003924e66efd5_zps1d639fad.jpg  
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