My MGB runs - sort of!

[pbsch]

I had it running only marginally better, so I decided to do some more basic troubleshooting. Since my fuel injectors were a bit of an unknown, I decided to flow test them. My methodolgy was pretty simple, pulled the entire injector assembly out of the intake manifold, rigged up a connector from a sacrificial harness I had laying around and ran the injectors at 12V on the fuel pump (figured it would give a good indicator of any other issues with fuel supply too) and caught 60 seconds worth of fuel spray from each injector...

Results

1 - 80cc 2 - 130cc
3 - 90cc 4 - 150cc
5 - 150cc 6 - 148cc

This is probably a big piece of my puzzle don't you think?

Looking at some conversion tables, the 17# injectors should produce 178cc of fuel at full cycle for 60 seconds - I'm nowhere close. With my modded intake, headers, cleaned up and polished intake and exhaust ports and free flow exhaust system, I'm wondering if the 17# injectors are really up to the task even if they are flowing the 178cc of fuel at high rpm. I have found a set of brand new delphi 21# injectors that I can pick up reasonably cheaply and am thinking I could just update my fuel injector size scalar for the bigger fuel injectors. What do you all think? Overkill? room to grow? buffer for diminished flow over time?

[pbsch]

For those of you with injector testing experience - does the 60 sec at 12V and full fuel pressure fairly closely test the true rating of the injector? Should I see 178cc this way if the injector is truly delivering 17#/hr? Thinking I'll test the new ones and see how well matched they are and whether they are truly 21# delivery...

BTW - witchhunter.com calculator says that for a 6 cyl engine producing 200hp (enthusiastic, I know) the injectors shuld be about 20.8#/hr which is why I was excited to find the 21#ers as cheaply as I did.

[robertisaar]

better to have them a bit too large than a bit too small.

an accurately timed 60 seconds at full voltage(more like 14, but that only really effects opening/closing time, which between 12 and 14 volts, is measurable in a couple of mSec) at a consistent pressure is a decent test.

i bet the pattern looked pretty crappy on 1 and 3?

[pbsch]

yeah, very similar to the kitchen faucet on a very low setting. For giggles I pulled the filters and backflushed them with some carb cleaner, now have them soaking in a product I use to clean the jets in my MC carbs in my ultrasonic cleaner. I'm going to pull them tomorrow and retest to see what sort of improvements I can get.

[TGP37]

I would say the inj 4-5-6 are close enough to believe they are flowing proper. You will loose some fuel to vapor drifting away.

I once put fuel injector cleaner into the fuel rail and then attached to fuel system. Turn over briefly to soak the injector insides in the cleaner. After 30 minutes or so, try to start. It will take a minute to start proper but the injectors will get a good cleaning on block that way. You can also pump carb cleaner through the injectors off block. Just look up the youtube video of it.

I had it running only marginally better, so I decided to do some more basic troubleshooting. Since my fuel injectors were a bit of an unknown, I decided to flow test them. My methodolgy was pretty simple, pulled the entire injector assembly out of the intake manifold, rigged up a connector from a sacrificial harness I had laying around and ran the injectors at 12V on the fuel pump (figured it would give a good indicator of any other issues with fuel supply too) and caught 60 seconds worth of fuel spray from each injector...

Results

1 - 80cc 2 - 130cc
3 - 90cc 4 - 150cc
5 - 150cc 6 - 148cc

This is probably a big piece of my puzzle don't you think?

Looking at some conversion tables, the 17# injectors should produce 178cc of fuel at full cycle for 60 seconds - I'm nowhere close. With my modded intake, headers, cleaned up and polished intake and exhaust ports and free flow exhaust system, I'm wondering if the 17# injectors are really up to the task even if they are flowing the 178cc of fuel at high rpm. I have found a set of brand new delphi 21# injectors that I can pick up reasonably cheaply and am thinking I could just update my fuel injector size scalar for the bigger fuel injectors. What do you all think? Overkill? room to grow? buffer for diminished flow over time?

[TGP37]

yeah, very similar to the kitchen faucet on a very low setting. For giggles I pulled the filters and backflushed them with some carb cleaner, now have them soaking in a product I use to clean the jets in my MC carbs in my ultrasonic cleaner. I'm going to pull them tomorrow and retest to see what sort of improvements I can get.

To add to my previous post about off block cleaning yourself. I did this once and didn't break anything, lol.

Get a baby meds syring at any drugstore. The injector fits nice a tight into the large side, the carb cleaner straw fits the other side.

The carb cleaner is under pressure close to the fuel rail pressures. All you need to do is apply 12v to the injector. I got an inexpensive monentary switch to pulse power on/off.

It is a good idea to apply pressure then pulse on/off to clean the injector well.

Just don't have loose wires that spark with carb cleaner all over your hands and equipment.

[pbsch]

watched some youtube vids and saw about backflowing them etc. Did all that and got zero improvement on those two - oh well, my 21# injectors should be here thursday so it really doesn't matter. Since I wanted to do something over the weekend, I decided to sheild all of the wiring between the ECM and the coil pack and the coil pack and crank position sensor - I understand that having the crank sensor wire twisted generally eliminates the need for sheilding, but it was a nice day and i had the materials available, so I did it anyway. Reading some posts by guitar enthusiasts, it seems that copper is good for EM interference and aluminum is good for RF interference, so I did both. First, i wrapped the wires with self adhesive copper tape from the hobby store used for stained glass and soldered a ground lead to it. Then I came back and wrapped it with aluminum foil and finally, covered the wraps with some nice heavy electrical tape - looked real good and continuty checked the shield afterward. If nothing else, I'll feel like I accomplished something this weekend. C'mon usps - get me my injectors!

[TGP37]

Run a wire from the shield to the block. Needs to be grounded to work, I did the same thing but used aluminum, no copper. Then wrapped with insulation then heat shielding

I felt like shielding was needed since my coils are up front and that meant a longer crank sensor wire pair.

Yeah, no need to try and clean the injectors since you got new ones coming. Don't forget to use new o-rings oiled.

[pbsch]

ahhh yeah, got the new injectors in last night and put the new prom in an holy tire spin batman. Lights em effortlessly in first and chirps em real good in second. I haven't logged this new prom yet, so I think I'll do some dialing in this evening, let it cool and put the new knock sensor in tomorrow. This thing may be a daily driver yet!

[TGP37]

ahhh yeah, got the new injectors in last night and put the new prom in an holy tire spin batman. Lights em effortlessly in first and chirps em real good in second. I haven't logged this new prom yet, so I think I'll do some dialing in this evening, let it cool and put the new knock sensor in tomorrow. This thing may be a daily driver yet!

Nice to hear, gotta love those moments of victory.

Did you swap out your fuel filter yet recently?


You may have had lean knock, from the bad injectors.