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Discussion Starter · #1 ·
Hey everyone, I'm currently working on a 1991 CRX hf that I sold to a friend several years ago and recently purchased back in pieces. Originally when I purchased the car is had a d15b7 in it and was still running obd0. After I sold the car the D15b7 took a dump on the guy and he pulled it out had it freshened up and installed a z6 head and bought a crx si transmission for and basically stopped there. I have been putting the car back together over the last couple months and everything is in. I have a p06 ecu chipped to p28 a full monotech obd1 conversion harness and a new distributor.

I've been working through some fuel issues with the car, it had old gas sitting in it for a while, and now I have got the correct amount of fuel pressure, spark, and timing the car still won't start. The issue is that when I crank the car over the injectors are all firing at the same time instead of pulsing 1342 with the firing order. The engine floods the plugs get wet and it wont start. When the injectors are unplugged the car will start off the gas already in the cylinders and run for maybe 5 to 10 seconds and then die again.

If anyone has any idea what could cause the injectors to all be firing at once instead of in sequence it would give me somewhere to start. I have searched and searched and couldn't find anything specific to this topic. I'm thinking that it could be an issue with the ECU since it controls the injectors ground. The injectors are not sticking it's as if on the intake cycle all the injectors fire at once instead of just the cylinder that needs the fuel.

If anyone could give me a place to start or some things to look for that would be great I'm at my wits end with this car ?
 

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BATSLOMAN GIVES NO FUCKS.
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resistor box installed?
 

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BATSLOMAN GIVES NO FUCKS.
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didn't see the conversion part.
 

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93 Civic HB SI
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Make sure the ground wires that control the injectors from the ECU are isolated from each other, and you dont have any shorts/rubbing together. Perform some good end to end circuit testing and look for evidence of shorting.

If one ground wire manages to touch all 3 others, they may act the same. Also, the drivers in the ECU are beefy enough to pull the load of all injectors simultaneously, so having a short across all of them isnt farfetched.

Honestly, come to think of it, I think that 4 pulses at the same time "may" be normal injector operation. They either all pulse together at the same time, or two pulse together in pairs, oscillating equal on time between pairs. I will scope my car tomorrow morning during coffee and give you confirmation.

This is pretty standard for port injected cars, almost all of them will inject either at the same time only letting a small amount of pulse/fuel flow take place, or they will pulse in pairs letting more fuel flow per pulse.

The theory is that you dont want to inject fuel directly into the cylinder while the intake valve is open, since liquid fuel droplets dont burn, only the fuel vapor does. You want small pulses adding a small amount of liquid fuel in the runner to pool up at the back of the intake valve, where the fuel can soak up the latent heat from the valve/valve seat/cylinder head, causing the fuel to flash from liquid to gas, so that when the intake valve finally opens it is drawing in as much gaseous fuel as possible. Engines dont run on liquid fuel, only vapor.

This is why colder engines need more fuel to start, there is less latent heat when cold available to vaporize the fuel, so more needs to be injected so more of it has a higher portion of it turning to vapor.

You will get less fuel vapor with an equal charge of fuel on a cold running engine vs a warm engine, therefore to increase the vapor content on the cold engine, you need more fuel, which also means some liquid fuel goes to waste until the engine warms up. Once the engine warms, you can pull injected quantity back, because it will run just as effectively and efficiently with less fuel when warm due to enhanced vaporization compared to cold.
 

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93 Civic HB SI
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No, injectors are ob1
Have you ohmed them out? Verify they are high impedance injectors?

If they read 2-4 ohms, they are low impedance and require a resistor box. If they are 10-15 ohms, they are high impedance, and the ECU can run them as is.

Are you sure someone didnt try to "upgrade" the injectors using some from another engine?
 

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is it running off a chip or stock mcu?

what cam sprocket are you using and what marks were used when mechanical timing was set?

are ect, iat sensors both plugged in?
That is also a good point. If ECT shows -40, maxed out range, that ECU is gonna DUMP some fuel.
 

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Discussion Starter · #10 ·
Have you ohmed them out? Verify they are high impedance injectors?

If they read 2-4 ohms, they are low impedance and require a resistor box. If they are 10-15 ohms, they are high impedance, and the ECU can run them as is.

Are you sure someone didnt try to "upgrade" the injectors using some from another engine?
Yeah all the injectors are almost dead on 13 ohms.
 

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Discussion Starter · #11 ·
is it running off a chip or stock mcu?

what cam sprocket are you using and what marks were used when mechanical timing was set?

are ect, iat sensors both plugged in?
ECU is p06 chipped to p28 got it off ebay I told them the setup and they were supposed to give me the correct basemap

ECT sensors are new oem Honda, iat sensor is plugged in also.

I'm running the Stock D16z6 cam gear. Timed it by using the marks on the side of the cam gear lined up with the edge of the valve cover.

An additional piece of info. The car had gas sitting in it for 4ish years that was bad and I got as much out of the tank as I could and put in fresh 91 octane. The fuel filter was also stopped up which had to be replaced. The injectors are not original to the car I got them with an entire intake manifold used.
 

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Sloppy Jalopy
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if you can for a quick test remove the J1 jumper on the ecu ..and see if it starts..

did you or your friend do the wiring changes when the dpfi was removed ?
 

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Discussion Starter · #13 ·
if you can for a quick test remove the J1 jumper on the ecu ..and see if it starts..

did you or your friend do the wiring changes when the dpfi was removed ?
Ok which is the j1 jumper?

Crx hf are mpfi from the factory
 

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Discussion Starter · #17 ·
Update:
Advanced the cam timing by one tooth from where it was set (I didnt put the engine together or time it but it looked right)

The car started. Still seems like it needs more timing though runs pretty rough doesnt have alot of power. The distributor is fully advanced.

Would it be safe to advance it another tooth and see if it gets any better or do I risk bending the valves?
 

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BATSLOMAN GIVES NO FUCKS.
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remove number 1 spark plug. insert coat hanger. rotate to tdc......does your timing match what the coat hanger says?
 

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Discussion Starter · #19 ·
remove number 1 spark plug. insert coat hanger. rotate to tdc......does your timing match what the coat hanger says?
Thats what we did. It doesnt have the lower timing mark guide for the cam. So it was lined up on the two lines on each side of the cam gear with the head surface. We advanced the cam one tooth. Now it runs, just listening to it though you can tell it still doesn't have enough timing
 

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BATSLOMAN GIVES NO FUCKS.
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its runs with 1 tooth advanced and distributer maxed out?

b7 block with z6 head? its going to be 4.5* out of time. If I remember right, a y7 cam gear will fix it, or an adjustable.

have you tried rotating it 2 teeth and seeing if the dist will run it in the middle?
 
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