'87 K5 Injectors not firing

[jrdecat]

So I installed an electrical fuel pressure gauge on my '87 K5 to keep an eye on things, but when I buttoned everything back up it wouldn't start. Here's what went down:

1. replaced OEM TB fitting with aftermarket fitting with 1/8" NPT outlet for sending unit
2. replaced hard line with rubber fuel injector hose
3. spliced into big red wire on steering column for constant power for gauge
4. spliced into pink wire on steering column for switched power for gauge
5. grounded gauge appropriately on dash
6. tried to start K5
7. cranked and cranked with no fire (fuel pressure gauge shows 11psi), drank a beer
8. bought a spark tester and tested for spark at distributor - lots of spark. Drank another beer
9. removed intake...no fuel from injectors while cranking...more beer.
10. tested red and white wires, 12v with key on so signal from ignition coil is good...upslope brewing company pumpkin ale...1 pint 7.7% abv
11. got really pissed at k5 because this is 3 days that it hasn't been running
12. searched 67-72 forum for answers...found things similar but none that addressed exact issue
13. ask the experienced forum members for help
14. HELP!?!

Any ideas on what to test next? Fuel pressure regulator, clog from rubber hose after the new TB fitting...any suggestions appreciated

[jrdecat]

...where are all the TBI experts?

[Boom]

What fires the injectors? Crank sensor? Cam sensor?

[rfmaster]

ECM fires injectors if it receives DRP signal from ICM (inside distributor).

But first things first.

Get your multi meter (DVM) out and make sure that you have 12 volts supplied to injector connectors. Depending on year you may have White + Green and Red + Blue color wires coupled into injector snap-on connectors. Red and White circuits should always have +12V when ignition is on. ECM controls green and blue wire circuits. During cranking you must have +12V at Red and White wire terminals. Check this by disconnecting injector connectors from injector terminals and measuring voltage relative to engine ground.

//RF

[jrdecat]

Originally Posted by rfmaster

ECM fires injectors if it receives DRP signal from ICM (inside distributor).

But first things first.

Get your multi meter (DVM) out and make sure that you have 12 volts supplied to injector connectors. Depending on year you may have White + Green and Red + Blue color wires coupled into injector snap-on connectors. Red and White circuits should always have +12V when ignition is on. ECM controls green and blue wire circuits. During cranking you must have +12V at Red and White wire terminals. Check this by disconnecting injector connectors from injector terminals and measuring voltage relative to engine ground.

//RF

Thanks rfmaster...but I did that in step ten, although I didn't specify that I was testing the injectors, so that was a lack of info on my part. Is it possible for the injectors to be receiving 12v but the ignition coil is still bad? Going to recheck all my grounds today. I know that a ring terminal came off from the fuel line clamp on the back passenger side of the intake manifold when I was removing the steel line, but I know I got it back on. It was the braided strap to the firewall. Maybe there were two? Where are all of the grounding points for these things?

[rfmaster]

Grounds are very important for the EFI! ECM harness gets its grounds at two locations - front by the thermostat housing and at the back side of the passenger side cylinder head.

If ignition coil was bad you would not be getting any spark. You said you have spark in your original post.

Check 4 pin plug that plugs into distributor body. Make sure that it is fully seated and latch is locked.

//RF

[jrdecat]

Originally Posted by rfmaster

Grounds are very important for the EFI! ECM harness gets its grounds at two locations - front by the thermostat housing and at the back side of the passenger side cylinder head.

If ignition coil was bad you would not be getting any spark. You said you have spark in your original post.

Check 4 pin plug that plugs into distributor body. Make sure that it is fully seated and latch is locked.

//RF

Thank you RF. I had read somewhere that you could still have spark, but the ignition coil could still be faulty...don't know if that's true or not, but the coil doesn't seem to be the problem. I'm going to leave the new coil in the box for a few days.

So I know I'm getting fuel to the TB, I know the injectors have 12v at the red and white wires, I know that the distributor has spark. I have not checked the pickup coil under the distributor cap yet. I made sure that I got that braided strap on the back passenger side cylinder head put back on, but tomorrow I am going to put the ring terminal under the fuel line bracket instead of on top of it.

I also disassembled the fuel pressure regulator today. The little bowl thingy looked like this:



It seemed to be a kinked plate welded in...poorly. There was lots of spatter and it just seemed like some kind of hack job. I cranked the motor to get the fuel pump to run and fuel went all over the place, so now I know that fuel is getting TO the fuel pressure regulator, but not past it. I tried dumping a little fuel in the reservoir between the injectors and fuel dripped from the injector tips so I feel that they are not clogged. I ordered a new Jet Performance adjustable fuel pressure regulator kit. This is as good of an excuse as any to get one of these. I figure that since I'm running a 383 stroker with high flow intake and 3" exhaust all the way back I could one day use a little more than 11 psi.

Even if a bad ground was causing my injectors not to pulse, I'd at least get a drip or two, right? I was getting absolutely nothing to the injectors. We'll see once the regulator comes in. Oh and the old spring in there was fine.

[rfmaster]

In the photo is a fuel pressure regulator cap - factory used spot welding technique to position its relative position depending on the spring tension. Think it of as position pre-load for the spring. This was done so that the pressure regulator would open and maintain 9 to 13 PSI working fuel pressure. A simple screw adjustable regulator was deemed too expensive and possibly lead to unwanted tweaking. So Rochester had to lock it out. GM used a flow through system - fuel pressure regulator is the last thing fuel sees before leaving injector pod on its way back to the gas tank. The tension of the spring is what regulates fuel pressure that injectors see before allowing fuel to spray. It is a very simple system which works remarkably well.
Once you get adjustable regulator you'll need fuel pressure gauge on the fuel supply line to adjust fuel pressure. I you have stock TBI pump you'll get about 12 to 15 PSI tops. However, you'll need higher pressure and custom programming to feed 383 in the future.

Fuel pod volume is under working fuel pressure and injectors opening allows pressurized fuel to spray into the TB barrels. Pouring fuel says nothing about actual injector operation. Injector operation is controlled by ECM switch circuits.

A word of caution when working with high pressure fuel - be very careful! Read rebuild kit assemble instructions. Make sure to clean all parts prior to assemble, remove old gaskets completely, never re-use old gaskets and seals! Whatever you do just take your time to do right.

//RF

[jrdecat]

Got stuck again today. I can't seem to get the fuel meter cover to seat properly on the fuel meter body. I looked over the diagram about 10 times and can't figure out what I'm doing wrong. The only thing that has me baffled is how to know if the injectors are seated in the bowls properly.

In the bowl goes the metal washer and then the large o ring. then the injector with the filter and small o ring gets pressed down in there. how do you know how far / hard to press those in. I pressed them in as pretty good and then put on the fuel meter cover gasket and tightened down all the bolts. Got a lot of fuel spray when I turned on the key so something isn't right.

The second issue is that I plugged a noid light into my injector plus and couldn't get them to light up when I turned the key, which is really weird as I had tested 12v to each of the red and white wires...so now I'm thinking ground wires again. It had been mentioned that the injectors get their ground from the back pass cylinder head to firewall and near the thermostat housing. I know I have the strap at the back pass firewall, but can't for the life of me find one near the thermostat housing, but I did find this:



and this:



From the looks of it, I should have 2 grounds up front G108, G109 and 2 grounds at rear G106, G110

The diagram is from a '93 so it may not be exact, but should all the grounds be either black or braided. Wondering what the yellow-ish wire should go to from my first pic.

Can anyone please post a pic of these grounding locations so i can double check? Also a list of all of the grounds I should have would be helpful.