2.8 Rail Pressure

[85_Ciera_Rebuild]

I think one of the reasons the other owner unloaded this 88 Berreta was due to this "problem," which Mr. I-Don't-Know mechanic threw parts at it....like TPS, like IAC...and then twitched with throttle plate setting.

Problem - Hard Starting after driving now...when first started in morning, it may konk out when first taking off, unless you massage accelerator pedal.

Test - Finally got ticked with it, so I put R-12 guage on fuel rail port....Zero pressure....then turned key on, fuel pump energized for two seconds, and took it up to about 20 psi, then dropped back to Zero.

Another Test - With engine warmed up, when heavy acceleration happens, a black cloud of smoke comes out of exhaust pipe.

Another Test - With engine at idle, rail pressure is 35 psi....when floored, pressure drops down several psi.

Question - Where is the check valve on the Fuel Pump side?

Possible Problem - Fuel pump regulator just about shot...yes?


I might add that when I installed a newer oil pump, this problem was masked since this pump brings about higher pressure, which means fuel pump is engaged sooner.

[dcjredline]

Not getting to 42psi = bad Fuel Pump/Regulator
Dropping Fuel pressure = Bad Check Valve or Leaking injector(s)/Regulator

Check valve is in the Fuel Pump

[85_Ciera_Rebuild]

Bad Check Valve

Ok...thx

[dcjredline]

Hey you dont quote me on that, it is just in my list of possibilities. That was a sarcastic hey you BTW

[85_Ciera_Rebuild]

list of possibilities.

Within next two weeks, I'll pull the lid off of that 2.8, and stick my thumb on the return line with pressure gauge hooked-up, and have someone turn the ignition key....this should rule out a check valve, unless an injector is dripping, which I doubt.

I have no doubt the pressure regulator is shot since vacuum changes does not affect it correctly.

Vehicle can get around 27 mpg consistently...which is over EPA mileage....so, if a single injector had loose bowels, this would not happen....plus the motor runs smooth...so the pressure regulator is most likely the problem....and plugging return line with thumb will give a heads up, before buying any parts.

[85_Ciera_Rebuild]

Mr. Goodwrency wants about $200.00 for Fuel Pressure Regulator....Auto Supply Stores around $110.00....but, there is a kit available online, but I have doubts this one is fixable...I'll find out in time.

So, its turn key, wait two seconds, then turn key to start position....a few extra starter rotations sometimes, but it starts up.....having good oil pressure most likely assists since fuel pump is energized when oil sender has some 6 psi acting on it...and when fuel pump is running, it goes va-room.

I did notice the motor sometimes over-revs when warm after starting it...most likely, this is related to rail fuel pressure not being consistent...

Soon as I get the 1984 Volvo up/running, I'll be working on Beretta's 2.8 Fuel Pressure Regulator...I'll report back findings.

[85_Ciera_Rebuild]

Pulled the top intake air plenum off of 2.8 motor...surprise surprise...

Vacuum line feeding MAP sensor was cut open...maybe that's why black exhaust under extreme acceleration.

Took off both fuel lines from rail, and shot compressed air thru each line....it leaks on both sides, so fuel pressure regulator shot craps on holding pressure.

Afterwards, checked each individual injector via blowing air into top side...no leaks.


Anyone know...do you insert all injectors into the fuel rails, then insert into intake manifold? I was going to use SuperLube on O-rings...any thoughts

[86euro]

Vacuum line feeding MAP sensor was cut open...maybe that's why black exhaust under extreme acceleration.

Anyone know...do you insert all injectors into the fuel rails, then insert into intake manifold? I was going to use SuperLube on O-rings...any thoughts

With a broken line going to MAP, I would guess it was causing more than one problem.

Injectors into rail... then the assembly into the manifold. I always just use a light coating of oil on the o-rings. And obviously, make sure the injector holes are clean and smooth.

[85_Ciera_Rebuild]

With a broken line going to MAP, I would guess it was causing more than one problem.

Vehicle runs fine....decent mileage...27 mpg plus....not a problem, in my book:rock:


I think there are several codes stored...maybe I'll fetch them before I start it again.

thx...

[85_Ciera_Rebuild]

make sure the injector holes are clean and smooth.

First time...for injectors...I assumed the rubber o-ring inserts into hole, but apparently, it seats at the hole-or a pinch inward-on intake manifold.

I used WD-40 and let it sit overnight...then took a round brush with "hairs," soaked in diesel fuel, and spun it by hand to clean up facing....then got a wool haired shotgun (10, 12, 16 GA) cleaner brush, put it on air drill, lightly soaked in diesel, and let it spin slowly in hole...not such a good idea.

Pressure Regulator was shot...I re-assembled it...and pressurized it....was holding 30 lbs after some twenty minutes later.

Still got to put back on top intake plenum...fix broken vacuum line....etc...etc

[85_Ciera_Rebuild]

Two problems with 88 Beretta 2.8 V6:

1. No vacuum to MAP sensor
2. Fuel Pressure Regulator not upto specs.

SES Codes:

23 Manifold Air Temperature Sensor Circuit: Low Temp Indicated.

33. Manifold Absolute Pressure Sensor Circuit

44. Oxygen Sensor Circuit (Lean Exhaust)

45. Oxygen Sensor Circuit (Rich Exhaust)



As can be seen, there is a relationship between problems and codes....but, if you throw parts at it, without knowing what was wrong, it gets expensive. I didn't look at codes, I used a fuel pressure guage and knew something was amiss.

Btw, I left fuel pressure gauge on vehicle after I replaced fuel pressure regulator...it still showed 30 psi after several hours.

Took a 27 mile trip....less than 50 mph...stopped in city to get some food...no SES light yet...before, it would come on, and go off, and come on, and go off....etc.

Bonus - Fuel mileage seems to have jumped up...too early to tell...but maybe by upto 5 mpg gain via less than 50 mph driving. Pay off parts ($100.00) within 5,000 miles.

Since I disconnected battery after getting codes, I wanted to take a small trip to set fuel data points...no heavy footing it...slow/easy.

[86euro]

I have a couple regulators if you end up needing one. They have been sitting in the garage for a couple years though.

[85_Ciera_Rebuild]

I have a couple regulators if you end up needing one


I bought a new Borg/Warner for $85.00...so it should be good for next 7 years or so.

Wind was blowing today, but drove 90 miles round trip and reset fuel average display on both legs....Max Speed 50 mph with cruise set most of the way...starting cold from driveway....some city and slower rural drive miles included in this...:

27.7
34.8

Fuel economy is up after fixing MAP and replacing Fuel Pressure Regulator....how much, I don't know for sure yet.

[85_Ciera_Rebuild]

Footnote - After doing a mileage mpg test, as based upon miles driven, and comparing it to digital displayed mileage, I think it would be fair to say that when the Fuel Pressure Regulator is not up to pressure specifications, the digital display of mileage will be off.

With higher control pressure, you will see higher mileage displayed.

With lower control pressure, you will see lower mileage displayed.

Hence, the ECM program is most likely based upon injector pulse width and mph samplings.

Currently, with new Fuel Pressure Regulator, and my driving habits, the digital display of mpg appears to be just about correct....over 284 miles....28.97mpg actual vs 28.8mpg displayed.

Vehicle runs fine...no more high or erratic idling (FPR)....hard warm starts(FPR)...and much lighter colored exhaust under extreme acceleration (MAP).