2.7i swap crank/start/run issues - RESOLVED

[NigelStu]

Just finished (well, almost) a 2.7i swap (87 es received 87 is head, harness and 153 DME), and am getting loopy going through the forums and ETM trying to figure out my no start condition. Cranks, but no fuel pump operation and no spark.


RESOLUTION/FIXES at the bottom of 1st post - Thanks everyone for the help!

I have referenced JLevie's very good trouble shooting guide that seems to be in every single no start thread, and have narrowed it down to no start signal getting to the DME, but I'm not seeing an answer to my question on how to fix the issue.

Following Jim's guide, everything checks out OK (power to DME 18, main relay 30/86, grounds all good) except that I do not have power to DME pin 27 OR 37 with key on. I do have continuity between the main relay and those pins.


So - 2 questions:

1. Just to confirm, when checking power to pin 27/37, key on, main relay in but DME unplugged so you can actually prob the pin (if this is wrong, how do you check it?...)
2. Assuming I did step 1 correct (unplugged DME to check), what are likely causes for no power to pin 27 and 37???? THIS is the info that I'm not finding in here.... I'm not sure where to look. ETM isn't helping me, but I might be looking in the wrong place?

I have tried multiple main relays, including a brand new one. But no help. CPS/DME/harness all came off of a running 2.5. Coil came off of the 2.7 that ran fine as well. Fusable link is good.

I have a feeling that I am missing something simple. Just cant see it. :?:

Thanks


For anyone looking for resolutions to similar problems...

THE FIXes
I had NO CRANK due to Black/Yellow start signal wire plugged into the wrong terminal. On a 4 terminal starter, the Black/Yellow start signal wire goes on the BOTTOM spade terminal (the one you can't see).

I had NO START due to:
1 - wrong main relay (relay needs to be 5-prong with two '87' terminals, not one '87' and one '87A). Order the correct one, it should have a white cap.
2 - C104 not plugged in. On 1987es --> 1987is swap, C104 contains the green wire which needs voltage for car to start. Plug it in to the normal plug, or if you want to pull the OBC (for a race car), then follow the steps in post #8. (note: I'm still confirming that with the OBC bypassed if the OBC relay box can be deleted as well. Confirmed: the relay box can be removed as well - and sold to fund your project!).

NO RUN:
AFM. Lesson learned, check part numbers for correct components. Just because someone selling a part says its for an 'is', check the part numbers... I had an 'es' AFM on the car. Put the old ugly looking "is" one on at it started and ran. Not great (hesitation with quick throttle opening, doesn't reach full RPM), but at least it runs.

Update - a bad AFM will allow idle, but not run right once you add part throttle (a good sign of an AFM problem is if car idles OK or can run at full throttle, but not at partial throttle). Swapped out AFMs with another 'is' AFM and the engine runs as it should now.



Summary:
-make sure everything is plugged in where its supposed to be.
-Check to make sure you have the correct relays in the correct spots
-Make sure you have the correct components for the system you are using
-One-by-one, check individual components with known good parts until you find the issue.


I hope this can help someone else.

[DaveSmed]

Next to the DME connector on the engine harness, there is a small white three pin plug. Is it plugged in?

[hotballs]

Next to the DME connector on the engine harness, there is a small white three pin plug. Is it plugged in?

This...everything you just said sounds like another language to me. Make sure that little (c104) connector is plugged in. Green wire is for fuel. Goes to another 3 pin connector inside your car on the body side. It's like the main gateway from the body side to the engine side for the fuel pump.

[jlevie]

Did the engine harness come off of a 88 or later car? If it did it won't have the C104 connector that routes the start signal to the DME and the tach & econometer data from the DME to the cluster.

Early cars route those signals from the body electricals to the engine harness via C104. Late I/IS cars (from 9/87) route them through C101. If you don't have a harness from a 9/86-8/87 I/IS, there are two possible fixes. One is reroute the wires to C101 and the other is to graft a C104 connector to the engine harness. You also need to make sure that the body side pin 20 of C101 isn't grounded when using a late harness. If it is the harness will smoke when the main relay closes. Grafting a C104 onto the harness is lots easier than adding those wires to C101.

[NigelStu]

The engine harness I have is an earlier one with the C104 plug (blue/green/white wire, correct?).

I didn't realize that one was needed for start; in the other threads I saw about C104 and the swaps, I read C104 was just needed to get the tach, speedo and fuel gauge to work.

I figured (hoped) that I was just missing something very simple. The entire dash is out (car is destined to be a ChumpCar), so no, C104 is not plugged in. I'll find the body side, plug it in and try to fire it up again.


Thanks for tips guys.

[hotballs]

Yeah i think your confusion was about that being connected to the "fuel Gauge," but that wire is the main fuel supply.

The other ones are for tach and MPG.

Detroit what. Go Redwings.

[NigelStu]

Green = go, right? How appropriate.... :???::roll:


I think where I got confused/missed a step is most of the info on these swaps involve a later harness. Those instructions were for splicing in the tach and mpg for the meter to work, but no mention of a main power wire (other than 'it goes through C101'). Since I'm not running the stock meter, I didn't care about the tach or mpg, so I didn't even bother connecting. I thought C104 was simply info coming OUT of the DME. I missed that bit on needing power going IN through the green wire... doh.



Next question - I'm not going to be using the OBC. Looking at page 1360-4 in the '87 ETM, it looks like I wont get a start condition without the OBC since it looks like the start signal goes through the OBC relay box - in at pin 4 on C2, out at pin 3 on C2. Is the OBC relay box needed for the car to run and work correctly? I'll plug in the relay box to get her started, but would like it out if possible. If the relay box is not needed, where is the best place / way to skip that box?

[DaveSmed]

Next question - I'm not going to be using the OBC. Looking at page 1360-4 in the '87 ETM, it looks like I wont get a start condition without the OBC since it looks like the start signal goes through the OBC relay box - in at pin 4 on C2, out at pin 3 on C2. Is the OBC relay box needed for the car to run and work correctly? I'll plug in the relay box to get her started, but would like it out if possible. If the relay box is not needed, where is the best place / way to skip that box?

You would be correct, if the car is wired as equipped with an OBC, it will not start if the relay box is unplugged.

Time to thank the Bavarians.



In this pic in the lower right hand corner, C104 is disconnected. Follow the body side harness to the upper left hand corner... Kinda looks like another C104 right?

It is actually that easy, thats all the OBC anti-theft harness is. Switch the plugs and you are good to go (and sell your uncut 13 button harness to recoup a little $)

[NigelStu]

Dave - Thanks for the pic and info on bypassing the OBC - I did that and power showed up at pin 27 on the DME.

My problem ended up being more than just that. Autopart store sold me the wrong main relay (87a type - was powering the fuel relay with key in off position, and then turning it off with key in run position....). Put the old one back in and now she at least cranks, has spark, and fires up for a few seconds.

And then it promptly dies. I am expecting (and hoping) that the pump just isn't picking up fuel (I ran the tank very low prior to starting the work, and car is currently sitting with the right side higher than the left).

Big smile and big relief when I saw the timing light finally blinking, and that wonderful sound of an engine firing for the first time! woot!

[DaveSmed]

Nice, glad it helped out.

E30 relays screw more people up.... I think there is only one standard style relay in the entire car.

[NigelStu]

Still don't have run condition. I have spark and crank, but it'll die shortly after it starts. I am NOT hearing the fuel pump in that crank time / 1 second run time. Power is present at the fuel pump relay 30, fuse 11 is OK. timing light is indicating spark.

Any ideas? is there something else that needs to be plugged in? Looking at the ETM, it appears there are 2 fuel related relays? One normal sized next to the main relay in engine bay and one taller one under the dash. Both plugged in, and I have swapped other same type relays into both locations without help.


Do the DMEs make any noise? Humming/buzzing? mine is....


Dave - clarification question. Is that bypass ONLY for the actual OBC, or does it bypass the OBC relay box as well? I currently have that plugged in.

[jlevie]

What is the rail pressure when trying to start the engine? Is there plenty of fuel in the tank?

[NigelStu]

Tank is low, but same fuel amount as when I drove the car into the garage a few weeks ago. The low-fuel light had turned on ~10 miles from my house. I parked it and started the swap. Car is currently sitting level

I'll have to check the FP at rail, but I'm guessing itll be zero psi since I'm not hearing the pump run. I know the pump doesn't run with key in 'on' position, but it should run while engine is cranking and running for that brief moment, correct?


I did not touch the fuel system as part of this swap, other than taking the hoses off the old fuel rail and putting them on the new rail. Car ran before, so I would think that the pump(s) wouldn't just fail in 3 weeks of sitting there.

[lateracer]

Yeah, this is a fun swap. I recently did the e to i swap on my lemons car, so I feel your pain. Mine was an 86e to a post 9/87 i harness with a 173 DME, so YMMV.

I got the brief start but no run condition. Mine turned out to be AFM related (broken wire near the connector needed to be repaired). If I unplug my AFM, it still does the same thing. Are you using your old AFM or have you switched to a different one? I don't think I and E AFMs can be swapped.

About the relay/fuel delivery situation: You're running a two pump setup on a one pump harness installed on a car that probably has an iffy electrical system to begin with. Basically, you're in waters that aren't frequently visited...it's what makes lemons/chump car fun, right?

I would highly suggest installing an inline pressure gauge and jumpering the fuel relay to see what happens. You may see good initial pressure that quickly dies as the motor starts to demand more fuel. I had my lifter pump go bad and then a few months later my inline. Having the inline gauge keeps you from having to guess at what your problem is, which is valuable in high stress environments like the pits at the track. Summit sells a liquid filled gauge for less than $20 that lets you know what kind of pressure you're getting at the rail while the motor is running. I can't say how much I love having that thing in place. In two seconds you can glance down and rule fuel delivery out as a problem source.

[NigelStu]

Fuel pressure is OK on the car. It was not the issue. AFM was (maybe still is)

Lesson learned - always check part numbers when buying or swapping parts. The AFM I had on the car was supposed to be a 'good working IS AFM', but turned out the guy sold me an 'es' AFM. Put the old crappy 'is' AFM that came on the parts car and it fired up and idled. Compared my old es part to the purchased part, same part # and circuit board. IS circuit boards look very different.


Car at least runs now. Starts right up, idles fine. Has some run issues. Quick throttle application will make it stumble and/or die. Seems anything over ~1/2 throttle will eventually make it break up a bit and stumble. Car will not rev all the way up to redline. TPS is adjusted correctly, and works per electrical tests at closed and WOT.

Will be checking for leaks, but is there anything else that is likely to cause run issues like that? AFM issues, CPS going bad? DME bad?

I'll repeat a question from earlier - are DMEs supposed to make any buzzing/humming noise?