Idles and runs terrible

[Laredo]

Actually, a bad diaphram will have the opposite effect, and will lean out the engine. The boost is supposed to push down on the diaphram to close down on the fuel return so it forces the fuel to the rail. That is how fuel pressure rises with boost. The FPR vacuum hose will tell the tale on that one.

Gotta disagree with you on a large part of this.

1) Yes, the boost pressure pushes the diaphram to close off the return flow, but....... during most driving conditions, you are not on the boost (non-boost light cruise, idle, etc) and the FPR is getting engine vacuum which is pulling the return valve open against spring pressure - thereby reducing injector pressure. With a leaking diaphram, the spring pressure would push the diaphram down and valve closed, increasing pressure and thus richening the mixture.

2) Furthermore, even in your boost scenario with the injectors going lean due to a leaking diaphram, the ENGINE would be rich because of the amount of fuel (at 40 psi) that gets pushed through the vacuum hose directly into the intake manifold. Under vacuum conditions it would be even worse because of even LOWER than atmospheric pressure in the intake. Been there, seen it.

3) Even though this car obviously had multiple problems (wiring, compression, fuel pressure), I was right on with the fuel pressure. Spec is KOEO is 40 PSI that should hold for 60 seconds after key off. Before the pump replacement, he had 30 PSI with a pressure drop immediately after key. Now he has the specified 40 lbs.

As for the fixing the cheapest, easiest things first - absolutely. but I was pretty sure about the fuel pump, seen it too many times.

[Laredo]

Would you please briefly outline proper procedure for cylinder pressure check.

Nothing hard or complicated about it as some would make it out to be. It is really quite simple. Put the piston at top dead center of compression stroke (both valves closed). Now you need to pressurize the cylinder with compressed air. My compression gauge has a detatchable fitting to attach my shop air hose, but a simple rubber tipped blow gun seated firmly in the spark plug hole will do. With the cylinder pressurized, listen for where the leakage occurs (hissing noise). If you hear the hissing out the tailpipe - check for a burned/poorly seated exhaust valve. In the intake manifold - check intake valve. In the spark plug hole of the next cylinder - check head gasket. In the crankcase (remove oil filler cap) - bad rings. Be careful on the last one because about 2-5% leakage past the rings during this test is normal.

With the drastic difference in compression measurements you had, I wouldn't worry about gauge calibration - it's all relative. If you used the same basic test conditions for each cylinder - you have enough info to determine the problem.

Good luck and let's hear the results!!

[835.0RS]

today i tried to drive the car and i found that when u hit about 3800 rpm it's like u hit a wall, it just falls on it's face until u let off of the gas. basically anywhere above about 8 psi of boost it does this. it will take off and run decent until the 3800 rpm wall. car has new plugs and wires. any ideas on this one?

[NavySVO]

Check fuel pressure vs. boost. You should get a psi for psi equivilent rise rate

[s8v40]

my brother had the same problem in his turbo coupe, it was a bad head gasket between #2 and #3 cylinders. Sounds like the same symptoms to me.

HTH

[NavySVO]

1) With a leaking diaphram, the spring pressure would push the diaphram down and valve closed, increasing pressure and thus richening the mixture.

Yes, you would be running a "little" richer during non-boost operations. The amount of fuel that would weep past a diaphram is minute, unless the diaphram is really torn.

2) Furthermore, even in your boost scenario with the injectors going lean due to a leaking diaphram, the ENGINE would be rich because of the amount of fuel (at 40 psi) that gets pushed through the vacuum hose directly into the intake manifold. Under vacuum conditions it would be even worse because of even LOWER than atmospheric pressure in the intake. Been there, seen it.

Boost pressure overcomes the small amount of fuel that would try to escape past the daiphram towards the intake. You wouldn't see a full 40+ psi right on the diaphram with boost acting against it, as the diaphram is doing large amount of work with minimal pressure, along with the aid of the spring.
Also remember that the fluid (returning fuel to the tank) will take the least path of resistance and return to the tank and not try and migrate towards boost (high pressure to low pressure).

Not trying to bicker on this, as I gather my info from a book written by Charles Probst, who holds a Masters in Automotive and Bachelor of Science. The book is written specifically for Ford FI systems with EEC III and IV equipage. He's also a buddy of Fleming, so I tend to lean even further in that direction.

[Laredo]

today i tried to drive the car .........

Have you addressed the compression problem yet? From what you have said before, you have a really sick engine. There is no majic cure to an engine with 2 cylinders at 50% of compression of the other 2. If the motor is actually that bad, it needs to be fixed. You cannot overcome major engine mechanical problems with tuning or more road testing. If you do have a head gasket problem, you are only going to cause more damage and problems by continuing to drive the car in this condition.

[NavySVO]

There is no majic cure to an engine with 2 cylinders at 50% of compression of the other 2. If the motor is actually that bad, it needs to be fixed. You cannot overcome major engine mechanical problems with tuning or more road testing. If you do have a head gasket problem, you are only going to cause more damage and problems by continuing to drive the car in this condition.

Absolutely. Address the issue now. A head gasket (providing it is the only thing wrong) is going to run about $100.00 after all the collaterals of good coolant, engine oil, etc........providing you don't have machine work involved with resurfacing head/block.
To me, $100.00 beats an entire rebuilt/engine replacement.

[835.0RS]

Yes we agree you are all very right about getting the bigger issue fixed first. We have not had time to start fresh and retest cranking pressure and leak down, and try to determine if a leak is between 2-3 cylinders.

What we think we do know is, we have no external leaks, or internal leaks (fluids) that is. The oil is clean and clear as very few miles on it. The coolant is oil free, there is no oil or coolant coming out the tail pipe, and it does not smoke any time. When running with the radiator cap off there is no sign of compression entering the system, as well when the dip stick is pulled there is a signifigant vacuum present. A side note here-it appears to not have a thermostat in it. It smells rich but not really visible black smoking. It makes no odd noises, and every once in a while for a few seconds it smooths out perfectly. When we put the code scanner on it and in the beginning when the scanner takes over running the motor for a minute or so it revs up and runs absolutely perfectly (the proverbial sewing machine smooth). When the reader quits/stops it goes right back to crappy.