[Formulas]

Its easy to inspect plug colors and condition, also you can figure if its systemic or a particular cylinder along with a compression check

if there is no outliers with these two things then something that effects all cylinders would be highly suspect

any MSD components involved here?

[JLMounce]

Originally Posted by Formulas

Its easy to inspect plug colors and condition, also you can figure if its systemic or a particular cylinder along with a compression check

if there is no outliers with these two things then something that effects all cylinders would be highly suspect

any MSD components involved here?

Yup, I'm pulling the plugs this week to inspect as well.

The system uses a Summit Racing billet distributor which is a copy of the MSD Pro Billet. It wouldn't surprise me if they were exactly the same.

MSD adjustable rotor, MSD Blaster 2 coil and on the electrical end the vehicle subsystems are powered via an MSD 4 channel solid state relay.

The ignition components listed above are about 3 years old.

[Formulajones]

Originally Posted by JLMounce

Yes, that's why I'm getting a gauge on it. I also need to run a datalog, but I'm a bit fearful of doing so incase something more major is occurring. I did notice last week that the system was struggling to maintain AFR at idle for a couple minutes. It would hunt to mid 15's where it's usually rock steady around 14.3. It cleared up after though. This could be a symptom that I was overlooking.
.

You probably won't want to try and duplicate it with a fuel pressure gauge installed either but if you do data log while you're at it. It'll provide more clues.

In the mean time if you have a laptop for tuning you could download the current tune and have a look at the learn table. If it's crazy high in the wot throttle areas like I mentioned that's a good indicator you have a fuel delivery problem and the unit is trying to cover it. That's one nice thing about these units is the safety they provide for things like that. Keeps you from totally destroying the engine at wot.

Not sure if you have changed your compensation limits in your tune but they are typically set at 50 percent which is a ton of fuel.

I usually turn them down to 10 percent or less in cruise and idle areas but the wot area I leave at least 25 percent just for situations like that.

[JLMounce]

Originally Posted by Formulajones

You probably won't want to try and duplicate it with a fuel pressure gauge installed either but if you do data log while you're at it. It'll provide more clues.

In the mean time if you have a laptop for tuning you could download the current tune and have a look at the learn table. If it's crazy high in the wot throttle areas like I mentioned that's a good indicator you have a fuel delivery problem and the unit is trying to cover it. That's one nice thing about these units is the safety they provide for things like that. Keeps you from totally destroying the engine at wot.

Not sure if you have changed your compensation limits in your tune but they are typically set at 50 percent which is a ton of fuel.

I usually turn them down to 10 percent or less in cruise and idle areas but the wot area I leave at least 25 percent just for situations like that.

I don't believe I should need to really get in to any RPM to determine if I have a fuel pressure issue. A quick tip-in and free rev should tell me if there's something going on with fuel delivery. At least if it's substantial anyway.

I do have the ProCal software that I can dig in to the tune. I don't have my learn limits turned down. On the FiTech's the long term trims can only go to 30%. I drive the car in such varying weather conditions and altitudes that it makes sense to let them have some play. I may have caught this quickly enough that it hasn't had much time to significantly alter the long term trims. It's worth a look though.

[gman005]

I had a similar problem with my Sniper. It was a bad injector.

[65madgoat]

Yes, bad fuel pump, bad injector, 02 sensor acting up can all cause EFI to dump more fuel under load or higher RPM causing misfire or loss of power

[JLMounce]

Had some time this afternoon to at least plug in the laptop.

The long term learn values for WOT are all very close to what the VE table is commanding. They are ranging from -5% at 5500rpm to +7% around 4000rpm, but most are within half a percent of commanded value. However, as I said, there may not be enough long term learn at these points as I haven't been hotroding the car much recently, mostly just cruising because the cold roads won't hold that much power.

What is happening however is that my cruise to moderate acceleration trims in the 1800-3000 rpm range are all extremely out of whack to the rich side. 35-75kPa load range in that RPM window has learn values over 30% in some places, with the highest values at higher loads. This is where the car is being driven the most and I think this does point to a fueling issue. Considering this is only apparent in this rpm range, I don't believe this would indicate and issue with the oxygen sensor. If that was the case I'd expect learn values to be crazy all over the place.

[grivera]

Have you looked down the barrels and confirmed all injectors are working?

[65madgoat]

But if a fuel pump is acting up, causing EFI to dump more fuel, all injectors could/would be working and not tell you anything by seeing they are all working at idle....

[JLMounce]

Originally Posted by grivera

Have you looked down the barrels and confirmed all injectors are working?

Yes, I've verified all injectors are functioning. No injector fault codes either.

[65 Lamnas]

To me, it sounds like an ignition issue.

[johnta1]

Have a vacuum gauge?

What kind of timing chain/gear do you have?

[JLMounce]

Originally Posted by johnta1

Have a vacuum gauge?

What kind of timing chain/gear do you have?

I can read vacuum through the FiTech handheld. That reading hasn't changed. I typically see about 14.5" when the engine is warm. I do have a mechanical vacuum gauge that I can test that against as well.

I can't be 100% positive, but I believe the timing set is what Comp Cams supplies with their complete timing kit. It's a double roller type. The engine had a 280H in it when I changed out the top end. It had the complete comp kit in it so I'm assuming it had the timing chain as well. I reused as there was no slack in the chain. I always estimated the engine only had a couple thousand miles on it when I purchased the car from the previous owner.

[JLMounce]

I spent the day working on the car and doing some testing. I wish I had a complete log but for some reason the log function in the procal software or on my handheld is not functioning. Might be something with the laptop I’m using.

Anyhow here are my findings.

Fuel pressure is running at 50psi at idle, it should be 58psi. On a quick rev it’s dropping to 40 psi. That’s definitely a problem.

Replaced the fuel filter and I honestly can’t say that the old one looked terrible. That clearly wasn’t the issue.

I verified all injectors are firing at idle and through the rpm range.
Verified timing has not moved. It’s still in sync with the computer.
Changed the plugs, two of them showed signs of the porcelain cracking. Most of them read hot and lean, which makes some sense.
Inspected the cap and rotor. Both look good with no indication of ionization issues. The adjustable rotor has not moved from where it was originally set.
Removed the valve covers and inspected each spring. No outward indication of the outer springs and what can see of the inner springs being broken. None of the polylocks have moved.
Finally also conducted a compression test. Engine at 190 degrees, full charge on the battery, throttle wide open.

1: 183
2: 180
3: 190
4: 182
5: 183
6: 180
7: 191
8: 192

What I was able to accomplish today made no difference in behavior.

There’s still way too much fuel in the tank to drop it, so I’ll need to drain some of the fuel. I also went ahead and ordered a genuine bosche fuel pressure regulator. I should be able to get to those next week. Hopefully there will be a positive result.

If not I’ll move on to checking the springs and inspecting the lifters.

[steve25]

I don’t know that 40 psi of pressure when it should be 58 is going to cut it under a load.

I mean that’s a 40% reduction in pressure which has to show up as a factor at high firing rates.

[JLMounce]

Originally Posted by steve25

I don’t know that 40 psi of pressure when it should be 58 is going to cut it under a load.

I mean that’s a 40% reduction in pressure which has to show up as a factor at high firing rates.

That’s also free-revving. It may be far worse under actual load.

The fact that it won’t hold 58psi at hot idle when fuel demand is at its lowest is why I’m also replacing the FPR.

[AG]

What is your CR?

[Formulajones]

Originally Posted by JLMounce

I spent the day working on the car and doing some testing. I wish I had a complete log but for some reason the log function in the procal software or on my handheld is not functioning. Might be something with the laptop I’m using.

Anyhow here are my findings.

Fuel pressure is running at 50psi at idle, it should be 58psi. On a quick rev it’s dropping to 40 psi. That’s definitely a problem.

Replaced the fuel filter and I honestly can’t say that the old one looked terrible. That clearly wasn’t the issue.

I verified all injectors are firing at idle and through the rpm range.
Verified timing has not moved. It’s still in sync with the computer.
Changed the plugs, two of them showed signs of the porcelain cracking. Most of them read hot and lean, which makes some sense.
Inspected the cap and rotor. Both look good with no indication of ionization issues. The adjustable rotor has not moved from where it was originally set.
Removed the valve covers and inspected each spring. No outward indication of the outer springs and what can see of the inner springs being broken. None of the polylocks have moved.
Finally also conducted a compression test. Engine at 190 degrees, full charge on the battery, throttle wide open.

1: 183
2: 180
3: 190
4: 182
5: 183
6: 180
7: 191
8: 192

What I was able to accomplish today made no difference in behavior.

There’s still way too much fuel in the tank to drop it, so I’ll need to drain some of the fuel. I also went ahead and ordered a genuine bosche fuel pressure regulator. I should be able to get to those next week. Hopefully there will be a positive result.

If not I’ll move on to checking the springs and inspecting the lifters.

That's kind of what I suspected, there is some sort of fuel delivery issue. That would have been visible in the tune as the unit tries to cover up the fuel deficiency. If it's dropping to 40 with just a quick free rev, it's probably plummeting fast under a WOT load.
Sounds like a possible fuel pump issue. What kind of pump setup are you using?

Edit: never mind I see you mentioned dropping the tank so you have an in tank setup. That's good news. Just make sure you get a genuine walbro. Not the cheaper stuff advertised as walbro on ebay. Those seem to have problems and I suspect they are reboxed garbage. I always just order directly from Walbro, I pay more but I know what I'm getting in the box. It's the same stuff all the OEM's use.
A trap door would have that swapped out in about 15 minutes, even with a full tank of gas Just sayin.

[Jay S]

Good looking pumping numbers for your altitude.

Sounds like you narrowed down the issue to fuel. Most likely the pump wore itself out and won’t pump enough pressure anymore.

[JLMounce]

Originally Posted by AG

What is your CR?

When I did the top end, I was able to get a rudimentary reading based on deck height, it's around 10.25:1.

Originally Posted by Formulajones

That's kind of what I suspected, there is some sort of fuel delivery issue. That would have been visible in the tune as the unit tries to cover up the fuel deficiency. If it's dropping to 40 with just a quick free rev, it's probably plummeting fast under a WOT load.
Sounds like a possible fuel pump issue. What kind of pump setup are you using?

Edit: never mind I see you mentioned dropping the tank so you have an in tank setup. That's good news. Just make sure you get a genuine walbro. Not the cheaper stuff advertised as walbro on ebay. Those seem to have problems and I suspect they are reboxed garbage. I always just order directly from Walbro, I pay more but I know what I'm getting in the box. It's the same stuff all the OEM's use.
A trap door would have that swapped out in about 15 minutes, even with a full tank of gas Just sayin.

Yes I always get a genuine TI Automotive pump from one of their distributors. Tanks Inc is an authorized distributor so I picked up on from there, along with a rebuild kit. New pigtail, feedlines, insulator, sock etc.

Originally Posted by Jay S

Good looking pumping numbers for your altitude.

Sounds like you narrowed down the issue to fuel. Most likely the pump wore itself out and won’t pump enough pressure anymore.

Yeah I'm thinking that's likely it. These numbers are pretty consistent from what I observed the last time I conducted a compression test about 5 years ago. There's a couple cylinders that are actually pumping a little harder. Could be that I've got a new battery in the car at this time.