View Full Version : Another SVO breaking up under higher boost

11-11-2009, 01:29 PM
Well, the car seems to be ok on low octane mode(9psi) but anything ore than that and it seems to fall on is face power-wise, possibly breaking up...I have yet to do a tune up(will do next week) other than plug wire an spark plug issues, what other causes am I looking at here? I read in other posts that sometimes the line going from the turbo outlet to the front of the intake collapses, except the line from the turbo outlet seems to be going to what looks to be a boost control soenoid...both lines look old bu I dont know what to replace them with if collapsing is an issue...vacuum line will certainly collapse, and for some reason I have a feeling finding OEM pieces is imposible

11-11-2009, 03:05 PM
the hose they speak of is the one going to the vam but replace all vac lines that are dry rotted first do the tune up that most likley will do it get new wires check tps .995 v and well go from there

11-11-2009, 05:16 PM
Oh, you must mean the air intake tube...now that makes sense, there is no vac line running between them...however looking at he vacuum line setup, I am confused, I have built these systems from scratch on other turbos so I like to think I have an idea of how it should work....on the compressor housing of the turbo there is a brass T-fitting(screws into the housing and has 2 outlets) one of these hose leads to the BCS(then from the BCS to the turbo inlet housing) the line runs directly to the wastegate actuator...which to me seems like it would limit boost to whatever the wastegate spring is(7psi maybe?) the wastegate would see boost directly from the compressor housing at the same time the BCS would...it doesnt look right to me, but according to the boost gauge it works

11-11-2009, 06:16 PM
TPS should be set to less than 0.900 VDC on the SVO at closed throttle. And make sure it will go to more than 4.50 VDC at wide open throttle.

11-13-2009, 01:28 PM
well, I got around to checking the air inlet tube, it doesn't seem to have a spring that I can feel from outside, but its pretty solid, it would take some truly massive vacuum to collapse it, I will check TPS voltages later tonight

11-18-2009, 04:41 PM
alright, pulled off the air inlet tube, still has the spring, TPS voltage is .9v closed an 4.6v open, changed the fuel filter, the car seems to be acting better, but under WOT at full boost the car still seems to fall on its face...however it seems to be fine up till 15psi...maybe the car is overboosting? its kinda hard to tell with the stock gauge...but even if it was boosting past 15psi, that shouldnt cause it to break up right? well, i guess the next question is whats causing my assumed overboost? one of the lines leading fro the BCS to the wastegate is behind one of the AC lines and over time seems to have been slightly crushed...just not sure that would be enough to throw the wastegate reading off....

another thing...I'm going to assume overboost here...what psi level would the stock pump no longer keep up? that of course would explain the whole poblem...I planned on replacing the pump with a walbro 255lph anyway

and one other problem that may somehow be related...hard starts...why am I having them? the plugs and wires are brand new and gapped at .035(which I assume is correct since thats what the old plugs were and that seems small) is thi possibly a bad coolant temp sensor causing all these issues?

11-19-2009, 06:49 PM
WHen you say "hard starts" - do you mean you have to crank, crank crank THEN if starts? That is indicitve of fuel pump check valve bad (read doesn't hold pressure).

IF SO - try this when starting;
Turn key on (will hear pump) trun off. Turn key on , will hear pump turn off. Turn key on THEN turn to cranking to start.

You might be changing th epump in the future anyway - but I would bet on blowing out spark (with that gap)


P.S. THese cars just don't have the hi energy discharge of newer cars!
Even at stock boost anything over .030 is too wide a gap!

11-20-2009, 02:56 AM
yes, thats what I mean by hard starting...I have a Walbro GSS 341 I have had sitting around for years that i have never had the opportuity to use since it wouldnt work with my other cars(its a nice high pressure unit which will come in handy), the GSS 340 s corect for mustangs, but with the fuel pump hanger assembly rather than an actual canister I believe this one will work just fine...I'll be changing it sunday and I will re-gap the plugs as well...one other question...the fuel pressure regulator...will a 5.0L aftermarket regulator bolt onto the SVO fuel rail?

11-22-2009, 06:08 AM
one other question...the fuel pressure regulator...will a 5.0L aftermarket regulator bolt onto the SVO fuel rail?

I am certain it will, I have a Holley Regulator on mine. It's and adjustable regulator and works well.

Let us know how it turns out today.


11-22-2009, 11:33 AM
well, after looking at the 341 closer, it looks like it wont work...so I'll sell it and get a 340, I will still re-gap the plugs though

11-28-2009, 04:45 PM
well, I re-gapped the plugs...no real difference...still breaking up under boost...so I am pretty sure its fuel related at this point...time for a new regulator

2 svo steve
11-29-2009, 03:03 PM
when I first bought my 84 in 89 I didd complete tune up. did not disconnect spout and had a very similar experiance ran awesome out of gear no load, loaded couldnt get it to burp loudly in prem mode.

11-29-2009, 06:39 PM
so how did you fix it?

2 svo steve
11-30-2009, 01:29 PM
Took it all back apart to square 1 forgot but I changed timing belt too that day.
reset all still ran horribly then remembered the spout conn at distributor disconn reset timing the found 1 cyl missing intermittanly found the cheapo bosch platinum cracked.
Installed a set of nippondenso plugs and she purred again.
If your timing has jumped or someone adjusted it this may lead to your answer.

I hate to tell ya but if the fuel pressure is normal and holds in the rail overnight it may be gunked up injectors too I had similar issue on my 86 thought it was the waste gate sticking replaced that and after much hair pulling and beers later I swapped them from my 84 it helped so drove it that way awhile till jegs sent a new set of much much larger flow profile. this created other issues but thier not related to you probblem.
good luck dont let it whip ya these cars are strange at first then become mundane after it all starts to click in the brain.

11-30-2009, 04:19 PM
well, I dont have a timing let yet(been working over the last few years on DIS cars) so I have no way to verify correct timing really and I dont even know the procedure for setting it...I do know it has a MSD coil from the PO, along with what looks like it might be a MSD TFI module(cant really see to tell, but it is red) so what procedure should i follow to do the timing on this car? I'll buy a timing light next week

2 svo steve
12-01-2009, 04:21 PM
It is quite simple but it would probbably be better for you to get a book or research it in the previous threads.
I havent been in here for awhile but there was a section on tech talk there will be more detailes there for you than I would provide just remember the spout is yellow wire out beside the distributor... as I remember I decided that to change the belt went far enough into the engine as the waterpump needed a change with the process.
No sense just replacing belt and setting base timing without flushing coolant and replacing thermo. and waterpump. Its just a piece of mind thing unless you KNOW these were recently done.
It will cost more in parts but if 3-9 months later they gave you trouble you would have wished you had done them too.
Kinda like getting an allignment with a new set of tires better to have done it!

03-13-2010, 08:06 PM
well, an update..I found my problem today...I had a feeling it was fuel related for awhile now and after dropping the tank and removing the stock pump I found the culprit...the fuel injection hose running from the tank up to to top of the sending unit had a tear in it...replaced the hose, dropped the pump back in and it runs great now

03-18-2010, 06:22 PM
Dude! That is AWESOME! You know I totally forgot that could happen! I have read about it on the SVOCA site and even dropped my tank recently and checked that hose but mine was ok. I sure wish I could get mine running right! It's been driving me CRAZY to the point that I won't even mess with it anymore!

Good for you dude!


03-18-2010, 06:47 PM
the funny thing is it happened to me with my turbo neon that I built and modified the fuel canister on as well and it never occured to me to check it...the neon though the car wouldnt even start

08-05-2010, 11:58 AM
Another problem that will cause the engine to buck and spit at higher boost is a cracked exh manifold, or a cracked turbine housing..........ask me how I know.