Adjusting Bosch 233 regulator

Tori

Active Member
Im under the impression you can adjust the Bosch 233 fuel pressure regulator.

Is that true, and what tool does it take to get down in there ? I cant quite make out what it takes, maybe a very thin flat blade screw driver ?
 

626gn

Well-Known Member
Cannot adjust that regulator unless its been modified. The old school method was to carefully crush the top to increase pressure.
 

Anthony P

sharing knowledge with those who care to listen
Bosch 233 fpr is not adjustable. some aftermarket vendors sold a 233 look-a-like that could be adjusted via the vacuum port with a small hex key or allen wrench. that was many years ago.

some folks literally crushed their 233 in a vise to increase base fuel pressure - definitely not a good idea.

the turbo trans ams used the bosch 237 fpr having slightly greater baseline and max fuel pressure.

As you are looking to increase fuel pressure, make sure it is correct for your combination. if wanting to set for typical 42 psi, vacuum line off, engine rpm at idle, I'd suggest using an Accufab or equivalent adjustable fpr.

stock 233 fpr yields a baseline of 34 to 38 psig, vacuum line off, engine idle------if just checking basic functionality......maybe this is too much info for your question.
 

Tori

Active Member
Thanks guys for the quick responses.

This is a bummer then, as i passed on buying a stock looking (which i need here in CA for ease of smog inspection) FPR when i was told some where, if you could see a screw down in side you were golden. The dealy-bob inside mine looked like it had a screw head of some sort.

Anyway,.... I need to lower my pressure, just installed a DW300 and am at 52# vac. line off.

Anyone have the elusive adjustable stock looking unit they want to sell ?
 
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mikestertwo

Well-Known Member
Anyway,.... I need to lower my pressure, just installed a DW300 and am at 52# vac. line off.
Anyone have the elusive adjustable stock looking unit they want to sell ?
If your pressure is too high with a 233 regulator then you have a restriction in your return line. The pump is too big for the return line to handle the extra flow. In the future if you want higher base fuel pressure which typically is 42 psi use a 237 regulator. They came on a lot of mid to late 80's front wheel drive GM vehicles.
 

Tori

Active Member
Thanks Mike, i wasn't after higher pressure .... but building the system to allow larger injectors.

How can you pin-point a restriction ? I did replace the rubber lines going to the tank when i did the pump
 

dynoman

Well-Known Member
Bosch 233 fpr is not adjustable. some aftermarket vendors sold a 233 look-a-like that could be adjusted via the vacuum port with a small hex key or allen wrench. that was many years ago.

Is this what you are talking about ? This came off my car when I switched to E85 & a complete new fuel system .

DSCN0506.JPG
 

Anthony P

sharing knowledge with those who care to listen
Is this what you are talking about ? This came off my car when I switched to E85 & a complete new fuel system .

View attachment 300793

Sam, that was someone's version of the "chopped top" 233's.

In the 1990's, Bowling Green Customs sold a spot on identical 233 fpr that was adjustable. Problem was the 5/64 allen set screw would get torqued on by strong fingers causing the threads to strip. then fpr settings were not repeatable and all sorts of performance problems ensued. Here is a pic from the BGC catalog in 1993. It was pretty crafty in the day if adjustments were made with a soft touch.

P1020789.JPG
P1020789.JPG
 

Tori

Active Member
Yea, i think it will. Most things just can't "LOOK" aftermarket. Doesn't sound like this will solve my high pressure issue, but i'm sure once that is resolved i'll need to be able to fine tune the pressure.
 

dynoman

Well-Known Member
It's funny to hear you guys talk about crushing the top of the regulator to increase pressure because that is how they set the pressure when manufactured . I work on the older equipment that makes GM's FPR . To set fuel pressure they pump a gasoline substitute through the regulator measuring flow & pressure then slowly crush the top until it comes into spec .
 
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dynoman

Well-Known Member
Yea, i think it will. Most things just can't "LOOK" aftermarket. Doesn't sound like this will solve my high pressure issue, but i'm sure once that is resolved i'll need to be able to fine tune the pressure.
Well , at least you could tell them it's the correct part number !!
 

Pronto

Believe nothing you hear and half of what you see.
Many have to modify the return line with the DW300 to be able to get a base line in the 43 range. You may be one of them.
 

Ttype6

Well-Known Member
Thanks guys for the quick responses.

This is a bummer then, as i passed on buying a stock looking (which i need here in CA for ease of smog inspection) FPR when i was told some where, if you could see a screw down in side you were golden. The dealy-bob inside mine looked like it had a screw head of some sort.

Anyway,.... I need to lower my pressure, just installed a DW300 and am at 52# vac. line off.

Anyone have the elusive adjustable stock looking unit they want to sell ?
There's only two ways to lower your fuel pressure. Buy a 255 ltr/hr pump or replace your return line.
And yet another person gets screwed by the DW pump.
A different regulator will do nothing for you.
 

Tori

Active Member
Many have to modify the return line with the DW300 to be able to get a base line in the 43 range. You may be one of them.

Thanks, l'd say i am too. Any suggestions on what to modify ? Or does it need a completely different / new return line ? I'm not gunning for any special low ET, just trying to get this thing to handle boost on 91 California fuels. 60# injectors are the next step.
 

Ttype6

Well-Known Member
Thanks, l'd say i am too. Any suggestions on what to modify ? Or does it need a completely different / new return line ? I'm not gunning for any special low ET, just trying to get this thing to handle boost on 91 California fuels. 60# injectors are the next step.
Installing this pump has caused a problem that can only be fixed by replacing the entire return line or installing a different pump with a lower volume of output. Was this problem mentioned to you in the sales pitch? If the pump is hot wired,removing it and drilling the Saginaw fittings in the return line might get you where you need to be but isn't a good way to go because the pump would receive lower voltage. If you had been given more information,you might have made a different decision and there would be no problem. Because you weren't given all of the vital information,all of you current options involve spending more money unnecessarily.
 

Anthony P

sharing knowledge with those who care to listen
As more details come to light from the OP, I agree with others noting this this not a fuel pressure regulator matter. I think the pause button needs to be pressed here and parts combination and application should be reviewed.

a DW300 pump flows 320-plus ltr/hr. I don't have fuel line size spec data at my fingertips, but that is a ton of fuel circulating and not being consumed by the engine. And the fuel pressure baseline reflects just that. Fuel temp rises by increased unused circulation leading to less thermal expansion on the combustion power stroke. Bottom line now is way too big a pump for current components as stated in post #16. Pressure does not equal flow --- rate or volume.

Tori,

it is unclear what your current combination of parts is relating to turbo, injectors, boost level, internal engine mods, girdle, etc. Is this car purely a street car or will it go to the track for some fun runs as well?

60# injectors will support 550 - 720 HP. Just saying you may want to review your current setup and where you want to go with respect to parts selection and corresponding performance levels. That pump is way to big for where the car is now. 60# injectors may be overkill for the desired performance level.

50# injectors will handle 450 - 600 HP with complementary components. TT chip would have to be modified with injector change. Anything in the mid-400 HP and up should be looking at internal engine upgrades (cam, billet main caps, girdle, etc) to support and complement the injectors, turbo, intercooler, etc with the boost levels required at this performance level.

Not enough information to make suggestions "other than a smaller pump as already stated.
 
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Anthony P

sharing knowledge with those who care to listen
Ttypev6 summed it up nicely. Component selection is key. no reason to buy parts that are overkill for what you are doing.

there are some good tech data tables on gnttype.org. if you are not already familiar with that site, go to the "Resources" drop down box and view the tech info articles. Below are two neat links to injector stuff.

http://www.gnttype.org/techarea/fuelsystem/injflow.html

http://www.gnttype.org/techarea/misc/lubrant.html

parts and technology has changed over the years. use those charts as an aid and then ask the forum here for advice. don't want you to be sold any more parts that are a complete mismatch to your setup.

the 255 ltr/hr pump as suggested with work fine with the stock fuel lines. that's 67.4 gal/hr, capable of supporting 750 HP. maybe a 255 pump is too much capacity still? more details on current setup and what you want to do are needed so that a good parts combination can be suggested.
 
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